How to clean ORP and pH probes

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Let’s face it: eventually the probes in a chemical controller will get dirty. Maybe it’s some calcification, or the usual oily organics that stick to the bulb. Whatever has dirtied the probe, you can bet your water chemistry readings will be distorted. In this article, we cover an easy way to clean ORP and pH probes.

Clean probes are essential to controllers

Pool chemical controllers rely on probes to tell the system what your water chemistry is. There are probes for Oxidation-Reduction Potential (ORP), Total Dissolved Solids (TDS), Free Available Chlorine (FC or FAC), Total Available Chlorine (TAC), and of course, the most common type, pH probes. As far as we know, every controller has at least a minimum of a pH probe, but most controllers also have ORP. The fancier controllers like the Prominent DCM5 have free chlorine and total chlorine too, which allow the controller to calculate combined chlorine (CC) in real time.

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This controller, the Prominent DCM5, has four probes. The far left one is a flow meter, then Free and Total Chlorine probes, followed by pH and ORP probes.
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When probes get dirty, their accuracy is diminished. Since these probes are submerged in flowing water, contaminants in the water itself can adhere to the probes themselves, and that’s the purpose of this article. Just imagine if your probes were sitting in a sample that looked like this:

How accurate can those probes really be? Just look at the sample water! As a pool operator, this should be unacceptable, because the controller is not going to have accurate inputs, which means chemistry is inevitably going to stray from the desired set points.

Cleaning procedure

You will need:

  • Three disposable or washable cups, or plastic containers, bowls, etc.
  • Distilled water (bottled water is fine)
  • A tiny amount of muriatic acid (use an eye dropper or syringe)
  • Safety gloves/glasses
  • SimplyPURE enzymes
  • Toothbrush (soft bristles)

First, fill two cups about halfway with distilled water. Add a few drops of Muriatic Acid to one of them using an eye dropper. The second cup should remain clean. In the third cup, add about 2 fl.oz. of SimplyPURE enzyme.

Second, close off the water flow to the probes, and follow the controller manufacturer’s recommended procedure before removing the probes. Most controller setups have an easy-to-find valve that simply shuts off the water to the probes.

Then, remove the probes that need to be cleaned, following the controller manufacturer’s recommended procedure.

Dip the probe in the enzyme, then brush with the toothbrush gently to remove oils and other ‘gunk’. This step alone may clean the probe sufficiently, but if there is calcium buildup remaining, proceed to the next step. If not, rinse the probe in the distilled water, and put it back where it belongs.

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If calcification is on the probe, submerge the probe in the first cup that has a few drops of acid in it. Keep it in for about 30-40 seconds. Brush with the toothbrush to remove calcium buildup. Repeat the enzyme wash and acid wash as necessary until the buildup is gone. Then rinse in the distilled water before putting the probe back.


Preventing calcium and organic buildup on probes can be as simple as using Natural Pool Products on a regular maintenance basis. NaturallyFREE is a scale inhibitor which will prevent calcium from forming on the probes (and should help prevent scale anywhere else in the system too). SimplyPURE enzymes will address the non-living organics, which should also help keep the probes clean, much like it helps keep tile lines clean.

Hopefully this procedure is easy enough to follow, and we hope to release a helpful how-to video on the procedure in the future. If you have more questions, please contact us, or your local NPP dealer.

How to manage Iron in Swimming Pools

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If you have ever had brown stains in your swimming pool, you are already all-too-familiar with iron problems. In this article, we discuss how iron gets into our water and why it creates stains. Then we will discuss options for managing iron to prevent problems like stains and excessive chlorine demand.

Metal Oxidation creates higher chlorine demand

Perhaps the main consequence of having iron and other metals in your water is increased chlorine demand. Metals are the easiest thing for chlorine to oxidize, and therefore the first things to be oxidized. As oxidants, metals like iron reduce chlorine rapidly. This is why at the beginning of the breakpoint chlorination curve (up to point A on the chart below), there is no noticeable increase of chlorine residuals until these “chlorine reducing compounds” like iron are conquered.

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The first things chlorine attacks are oxidants like metals. Iron is at the top of that list.

Pool operators with iron issues may notice a higher consumption of chlorine, but often it is overlooked. The cost may not be noticeably higher because the pool might be constantly introducing new water with iron in it. In other words, it’s the baseline, and nothing to compare it to. But rest assured, iron absolutely reduces free chlorine in water. Below we will discuss ways to control metals like iron, but first, let’s talk about where iron comes from.

How does iron get into water?

Iron is found in almost all natural water sources. According to a drinking water equipment manufacturer, LennTech, iron is in seawater, rivers, lakes and groundwater too. It up to those of us who manage and treat water to remove it. So iron usually gets into our swimming pools via the tap water. Certain areas of the United States have more iron in their tap water than others. For instance, the upper midwestern states (Ohio, Michigan, Indiana, Illinois, Wisconsin and Minnesota) are challenged with notorious iron problems. Swimming pools in those areas must deal with high levels of iron out of the faucet, or be plagued with iron staining.

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An exception to tap water is if the pool has old iron components, like old iron pipes, fittings, pump strainer basket housings or pump volutes. If these components have been worn down (like having low pH water flowing through them long enough), iron is sure to find its way into the pool.

There are some exceptions for other metals too, like copper. Copper can get into water from products like copper algaecide, mineral disinfection systems, and from corroding heat exchangers or copper pipes. Pools have turned green from copper before, and sometimes it is mistaken for algae. But let’s get back to iron.

Dissolved iron in water is mainly present as ferrous hydroxide (Fe(OH)2+). We could try to explain the chemical formulas and reactions, but you can read these three sources if you are interested in that level of detail. Source 1, Source 2, or you can go down the Wikipedia rabbit hole as we did. But for this article here, we will try and keep this as simple as possible.

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Usually, iron gets in our swimming pools in a dissolved, soluble state. This means it is mostly invisible and not yet oxidized. If drinking water is chlorinated or chloraminated, however, some of the iron may become oxidized and have a tinge of brown color to it. Iron, when oxidized, turns reddish-brown, and chlorine is consumed (reduced) in the process. If the iron was not yet oxidized in the pipes en route to the swimming pool, it sure will be when it is met with chlorine or a secondary oxidizer like ozone.

Oxidation is what creates staining.

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Oxidized iron stains usually present themselves first near return inlets.

Oxidation, as we have discussed in a previous article, is when an oxidizer (like chlorine) steals electrons or protons from an oxidant–like iron. So the key to preventing iron staining is to prevent iron from being oxidized. And to do that, we have a couple of options.

How to prevent iron staining

We can try to remove iron, either from the source water or from the pool itself, and/or we can chemically manage it by using a chelating agent or sequest.

Filter Iron out of the tap water

Iron filters exist and can be installed on pool fill lines. They do need to be replaced periodically; no filter has unlimited capacity. Such iron filters have a wide range in price depending on the removal rate you need, and the flow rate of your water. For instance, a 2″ fill line on a commercial pool will need a larger, more expensive iron filter than a garden hose filling a residential pool.

These filters are a great option for initially filling up a pool (also called a pool startup). The iron–and other metals that may be present in the fill water–will be filtered out prior to adding chlorine to the pool.

Remove Iron from the pool water

If your pool is already full and is challenged with iron problems, there are options to physically remove iron from the pool. Most solutions in the pool business are a two-part process. The first part is to sequester the metals–which basically means to cluster metal ions together into larger particle sizes–and then use a filter that can capture the sequestered metals. Such products do exist on the market already.

If you have a D.E. filter, it could be sufficient in and of itself to capture sequestered metals. Removal would be as easy as doing a media replacement. This method has difficulty removing already-oxidized iron, however. Ferric iron, for example, is not as easy to sequester as ferrous iron. More on that in a moment. In order for this plan to work on existing stains, you would need a way of lifting those stains and getting iron into a state where it can be more easily sequestered or chelated.

Chelate or Sequester iron to prevent oxidation

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Chelants like NaturallyFREE binds to (and isolates) individual ions, whereas sequestering agents cluster multiple ions together.

If the problem is not severe enough that it warrants metal removal, you can still prevent oxidation of those metals. Both sequestering agents and chelating agents can bind to metals and hold onto their protons or electrons. If stains already exist, sequestering and chelation is more difficult because the metals are already oxidized and insoluble. An additional step of lifting the stain back into suspension is necessary. To do this, consider using citric acid (also called ascorbic acid, or vitamin C).

naturally free scale and metal sequest

Our chelating agent NaturallyFREE is proven to chelate ferric and ferrous iron, but it is very slow to remove stains. It also works better in warmer water. If the water is colder than about 60ºF, the product will be very slow or even dormant. Keep this in mind when using NaturallyFREE.

Sequestering and chelation do not remove metals from the water. They just bind metals to prevent oxidation and staining. You would need some sort of filter to capture and remove the metals. As mentioned before, Regenerative DE filters can capture chelated or sequestered iron. We have even seen it happen on sand filters, but only a few times.


Stains occur when metals get oxidized and become insoluble. Otherwise, metals like iron are in solution or suspension, and mostly invisible. Metals are introduced to our pools through the tap water, with few exceptions like copper algaecide or corroded metal equipment in the pump room. The options to solve this problem are either a strategy of removal, or chemically isolating the metals to prevent further oxidation. In either case, if stains are already present, a citric/ascorbic acid might be needed to lift the stains. Contact us if you need help deciding what to do.

Starting a Commercial Pool Enzyme Program

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Busy, heavily-loaded pools tend to have a lot of bather waste. Swimmers shed sweat, body oils, and yes, urine; and those are only the natural forms of body waste. Let’s not forget lotions, cosmetics, sunscreen, deodorants and the like. All of these non-living contaminants are forms of organic waste that chlorine must oxidize to remove from the water.

Unfortunately, chlorine is not an efficient oxidizer.

Chlorine, specifically its strong, killing form of Hypochlorous Acid (HOCl) is an excellent sanitizer and disinfectant. It is a relatively weak oxidizer though, as it gets reduced rapidly. Because of this rapid reduction of chlorine, we find it prudent to supplement chlorine with enzymes and [if possible] a secondary disinfection system like UV or Ozone.

Related: ORP vs. Free Chlorine: Which is more important?

Commercial Pool Enzyme Program

Before explaining the benefits of using enzymes in swimming pools, let’s first distinguish between different types of enzymes. There are many enzyme products in the aquatics business, and most of them are made for residential pools. But can you think of a residential pool that has even a fraction of the bather load and demand of a busy commercial pool? If so, they are the exception, not the norm.

Commercial pools need an enzyme that is made for the job; an enzyme that is strong enough to handle the demand and also hold a residual over time. Otherwise, you’re wasting money and still not getting results…we know this because so many of our customers who have switched to Natural Pool Products have told us so. It may be hard to appreciate the difference until you see it for yourself.

Related: Organic Waste and Carbon Management (Pillar 2)

How enzymes work

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Enzymes are protein and amino acid compounds that catalyze reactions. They pull in a specific type of substance or compound, force a reaction–usually either a combining or separation of molecules–and release. We call these substances substrates. A good commercial pool enzyme will target non-living organics (carbon-based bather waste) substrates. They break the carbon bonds and metabolize them into carbon dioxide (CO2). The rest gets broken down and digested.

Benefits of enzymes in pools

prominent controller enzyme, nsf 50 enzyme, nsf 50 chemical, pool chemicals, natural pool productsAs mentioned before, without an enzyme, chlorine is held responsible for all of this bather waste. And while chlorine is excellent at disinfection, it gets used up quickly and inefficiently when fighting bather waste and oils. Enzymes, however, devour them. Enzymes are an affordable, safe and easy supplement to help keep your pool water clean and clear. Especially for the heavily-loaded pools.

Another thing of note is NSF/ANSI Certification. The Model Aquatic Health Code mandates an NSF-50 or NSF-60 certification for commercial pool chemicals if such chemicals do not already have an EPA registration number. All Natural Pool Products are NSF-50 certified, including our enzyme SimplyPURE.

Starting an Enzyme Program

concept plus, prominent pool, natural pool products, simplypure enzyme, simply pure enzyme, commercial pool enzymeThe initial dose of SimplyPURE enzymes is one quart per 10,000 gallons (32 fl.oz./10,000 gallons). This should be applied to either the surge tank or directly into the gutter. The idea is to put the enzymes directly into circulation so they spread around the pool quickly and evenly. Sure, you could pour them into the pool, but they will not circulate as fast.

After the purge dose, we recommend a weekly maintenance dosing of SimplyPURE based on the volume of water you have and more importantly, your bather load. The starting commercial pool enzyme dose is 10 fl.oz./10,000 gallons per week. The truth is, however, many commercial pools don’t even need that much. Our recommended residential pool dose of 5 fl.oz./10,000 gallons per week is often enough. Start with 10 oz/week and dial it in from there. You may find your pool can get away with less and still have great results.

We strongly recommend using a feed pump for SimplyPURE, to automate the dosing. Prominent makes a great feed pump called the ConceptPlus pump. Many of our customers use it, and can even control it using their Prominent controller itself (see photo above of the Prominent controller). For easy math, try 7 fl.oz./10,000 gallons per week, so it’s just 1 oz/10,000 gallons per day. Automation is a beautiful thing.

Here’s a video showing how to install a stenner pump, and we will also create a video on how to install a Prominent Concept+ pump as well.

How to Avoid Plaster Dust on a Commercial Pool Startup

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Let’s talk about a commercial pool startup. Not sure about you, but brushing plaster dust in the middle of a big pool is not enjoyable to us. Maybe that’s just us, and we are not pool builders.

Plaster dust is not just an annoyance, it’s actually a symptom of a more significant problem. Consider this: every speck of plaster dust you see is calcium that should have hardened within the plaster surface itself. In other words, you are looking at calcium that was stolen from the surface, and can never be put back. If your pool has a lot of plaster dust on startup, it is evidence of early damage and weakening of the plaster.

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Commercial Pool Startup Process

There are many ways to start up a pool. They range from just filling with water and doing almost nothing, to filling and hitting the water hard with muriatic acid to burn up the dust. There is also the industry-standard 30-day startup procedure, as published by the National Plasterers Council (here). The NPC startup is better than winging it and is full of good information. That being said, we have developed a method we believe is even better, and can prevent plaster damage from the beginning. It is called The Orenda Startup™.

Rather than trying to adjust the water chemistry after the pool is full, the Orenda Startup is proactive. It involves testing the fill water before the pool is even completed, so you know what chemicals the water will need. You see, water is almost never LSI-balanced out of the tap. If the fill water is aggressive, you can count on plaster dust and the pH spiking for the first several days of your pool startup. That is not only an annoying problem but a costly one too. Think of all the repeat visits; the cost of all the acid you continue to add to bring the pH back down; the time it takes to brush the pool to lift the dust. And even with all that, for large commercial jobs, can you even brush the middle of the pool?

When you test the tap water for the LSI factors (pH, alkalinity, calcium hardness, water temperature, TDS and cyanuric acid), you can input those factors into the free Natural Pool Products app.

Download our free LSI dosing calculator app Natural Pool on iOS or Android

The Natural Pool app will show you the LSI value of the water. Use the calculator to adjust the LSI on the right side of the calculator to +0.20 to +0.50. Ideally, +0.2 something. We recommend calcium hardness to be a minimum of 300 ppm, and alkalinity a minimum of 100 ppm. Tap “Get Dosage” and the app will tell you exactly how much calcium chloride and sodium bicarbonate you will need for the startup.

Add calcium or bicarb while filling (but not both)

Depending on what your tap water chemistry is, you will add either pre-dissolved calcium chloride or sodium bicarbonate as the pool fills. In most cases, calcium goes first, unless you have around 300+ ppm calcium out of the tap. In that situation, add bicarb as the pool fills. On the second day, add the other chemical to achieve the desired LSI. Never add these two chemicals on the same day. they will cloud up because they are incompatible. It’s bad enough on a residential pool; the problem is only magnified on a commercial pool startup.

Commercial Pool Startup Chemicals Needed

Natural Pool Products makes two chemicals that will be necessary for the startup, in addition to the usual commodities: calcium chloride, sodium bicarbonate, muriatic acid.

naturally free scale and metal sequestChelating Agent: NaturallyFREE

The first and most important chemical is our chelating agent, NaturallyFREE. NaturallyFREE is an alkaline substance that is compatible with all pool surface types, can be added immediately as water begins filling the pool. There is no need to wait until the pool is full, or half full, or whatever other sequestering agents require. Another benefit to using this product is it contains no phosphates, which will be handy down the road if and when you decide to remove phosphates. Especially for a commercial pool startup, getting off to the right start (without problematic byproducts like phosphates) is critical.

A chelating agent is important on any pool startup, especially when adding calcium chloride on the first day. It isolates each ion of calcium by grabbing onto its electrons, which prevents calcium (Ca++) from binding to Carbonate ions (CO3– –). Their valences are perfect opposites, so they attract. But if NaturallyFREE has time to chelate the calcium, it is no longer available to attract with Carbonate ions, therefore inhibiting scale.

Without chelating (or sequestering) calcium, adding it as rapidly as we want to could create some carbonate scale during startup, and that’s no fun. This product needs to be added on fill-up day, regardless of which order you put calcium and bicarb into the pool.

Enzyme: SimplyPURE

simply pure enzyme pool cleanerOn the second day, once the pool is full, you will add the second chemical (usually bicarb), along with a purge dose of our enzyme, SimplyPURE. This enzyme helps clean the water by removing non-living organics and oils, which are surprisingly common during startup. We are not sure why, but countless startups have visible oil slicks on top of the water as the pool fills up. Since we are not chlorinating the pool for the first few days, keeping it clean is important, and our enzymes are perfect for the job. And, when chlorine is first added, it will have a significantly reduced organic load to manage and can get right to the job of sanitization.

Another reason to add SimplyPURE on a commercial pool startup is for cleaning out the pipes when the equipment is fired up for the first time. We have never seen a pool construction site that does not have dirt and debris around. It is inevitable that some of this can get in the pool, pipes, and equipment. Enzymes help remove some of it; or, if nothing else, can help dislodge it from inside the pipes and get it trapped in the filter for backwashing. It is an affordable insurance practice to get the pool of to a nice, clean start.


Starting up a pool is critical to the life and longevity of the plaster surface. The LSI is almost always low out of the tap, so we are faced with a choice. We can either balance the water up front, or we can let it find LSI balance on its own (at the expense of calcium in your plaster).

To do our proactive, dust-free startup, follow these basic steps below, or read this procedure from the Orenda website.

  1. Test the tap water, and input values into the left side of the Natural Pool app’s LSI calculator.
  2. Adjust dials [on the app] to decide on the desired startup chemistry, with an LSI between +0.20 and +0.50. Ideally +0.2 something, with a minimum of 300 ppm calcium, and 100 ppm alkalinity.
  3. As the pool begins to fill up, add the purge dose of NaturallyFREE to the pool (32 fl.oz./10,000 gallons).
  4. Gradually add pre-dissolved calcium chloride (or bicarb) as the pool fills up until the desired amount (prescribed by the app) has been added.
  5. The next day, purge the pool with SimplyPURE enzymes (32 fl.oz./10,000 gallons) and add pre-dissolved sodium bicarb (or calcium chloride).
  6. Startup the equipment and proceed with everything else as you would normally.

Contact us before you try this the first time. We will help you dial it in for your situation, as every pool is different. These are just guidelines. Good luck!

ORP vs. Free Chlorine: Which is more important?

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Pool sanitization is essential

Swimming pools (especially heavily used public pools) can have serious demands put on them. Keeping water sanitized is paramount to people’s health and safety, but it is not always easy to do. Disease outbreaks like cryptosporidium can happen, and people sometimes get sick. Thankfully, chlorine is an excellent sanitizer. And chlorine is easy to measure in water. We can test free chlorine, total chlorine, and from those two, we can calculate combined chlorine. But how do we know if the chlorine we have is effective in our water?

We measure chlorine’s effectiveness in real time using oxidation reduction potential (ORP).

What is ORP?

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ORP and pH probes

ORP stands for oxidation-reduction potential. ORP is a measurement, in millivolts (mV), of the water’s potential for oxidizers to steal electrons from another substance. In the pool industry, chlorine is usually the primary oxidizer, and contaminants like metals, ammonia, and non-living organics are the targets of oxidation.

ORP is measured by a probe in a small sample of flowing water, usually next to your chemical controller. An ORP sensor consists of an ORP electrode, and a reference electrode. Basically a signal is sent between them which determines the potential speed of electron transfer. In other words, the oxidation and reduction potential. So let’s quickly discuss what oxidation and reduction mean, because “oxidation-reduction” are not the same thing; they are opposites. We get the following two definitions from this source.

What is Oxidation?

Oxidation is the loss of electrons by an atom, molecule, or ion.” Often, the lost electrons are replaced by oxygen.

What is Reduction?

Reduction is the net gain of electrons by an atom, molecule, or ion.”

This means that electrons transfer from one thing to another. The rate of electron transfer is measured in millivolts as ORP.

Since electrons (e-) have a negative charge, when they are stolen by an oxidizer like chlorine, they reduce it. Chlorine is reduced to Cl-, which is a chloride ion. Chloride can no longer oxidize, because it cannot attract more electrons.

Free Chlorine

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Advanced chemical automation controllers like ProMinent’s DCM5 can measure ORP, chlorine levels, pH and more.

Every certified pool operator knows to measure free chlorine. Operators should also measure total chlorine and calculate combined chlorine. Such information gives operators an idea of the sanitizer levels in their water, and can adjust accordingly. Say there’s a swim meet with a much higher-than-normal bather load. It will most likely take more chlorine to accommodate the demand. Even if you’re treating the water with enzymes, chlorine still has contaminants like ammonia to oxidize…so measuring chlorine levels is important.

Nowadays, quality chemical controllers can read chlorine levels and calculate combined chlorine automatically, as well as measure ORP, and control both ORP and chlorine levels as needed.

But without knowing the ORP, we don’t know how effective the chlorine is. That’s why we strongly suggest measuring and documenting both ORP and chlorine levels. We would argue both are important, but of the two, ORP is more important. Your pool can have 1.0 ppm free chlorine and 800 ORP with the use of enzymes, UV/Ozone or HDO. We have seen it happen. We would argue that’s better than 4.0 ppm chlorine and the same 800 ORP. If less chlorine has the same sanitizing and oxidizing power as more chlorine…why would you want more than you need?

Ways to optimize pool sanitization

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You know by now that we manufacture NSF/ANSI-50 Certified enzymes to break down and remove non-living organics. With enzymes, chlorine has less carbon-based bather waste in the pool to oxidize. Less oxidant demand means more residual chlorine to conquer other contaminants, so on and so forth. Enzymes help optimize pool sanitization, water clarity and overall water quality.

Secondary sanitation systems like UV an Ozone also help chlorine. There are secondary oxidation systems like Hyper-dissolved Oxygen (HDO) and Advanced Oxidation Processes (AOP). With the exception of HDO, these systems are point-of-contact systems that only work with the water they touch, which circulates through pipes in the pump room. Enzymes and HDO are out in the pool alongside chlorine the entire time. The bottom line is this: pool sanitization is critical in swimming pool management, and the ORP is the best metric to measure sanitation power. If you can have great ORP with a minimal amount of chlorine, that’s the best of both worlds.

The Undeniable Importance of Calcium

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Last week we got a phone call from a long-time customer of ours. They had just renovated a commercial swimming pool for a Homeowner’s Association (HOA) community.  The plaster was scheduled to be done the next day, and they called to ask us for help with their startup. Their primary goal was to protect the surface for the customer, and at the same time, minimize plaster dust so their people did not have to visit every day to brush.

This customer had heard we know how to prevent plaster dust…and we do. Why? Because we have a few core beliefs about water.

Core belief #1: Pool Chemistry should be LSI-Based

If you test for pH, alkalinity and calcium only, you’re missing half the equation for true water balance, according to the Langelier Saturation Index (LSI). When managing pool chemistry, what are you chasing? For most people, it’s what we call “range chemistry”, which is keeping those three values (pH, total alkalinity and calcium) within ‘ranges’ set forth by industry textbooks. But have you noticed how difficult it can be to keep pH and alkalinity consistent? They are always moving targets…and that’s not unusual.

You see, pH is a natural phenomenon. As long as there has been water, there has been pH. The pH of water impacts almost every other aspect of water chemistry. Yet it’s always moving, because it’s an equilibrium that can be affected easily by products like acid or soda ash. So instead of chasing the moving target of pH, we believe you should be chasing a more all-encompassing target: the LSI. The LSI can be driven by your best friend in water balance, calcium hardness. Unlike pH and alkalinity, calcium hardness does not change easily, and it helps keep your LSI more stable.

For more on why we prioritize LSI before range chemistry, read this.

Core belief #2: Water will seek equilibrium

Unlike #1, which is our opinion, this is a fact. Water will seek equilibrium, both physically (think of plumbing and how important gravity is), and chemically. Water wants to be balanced, and will stop at nothing to get there. Because of this, we believe you have a choice: give water the chemistry balance it craves, or it will steal it from anywhere it can.

In swimming pools, we’re primarily talking about calcium hardness first, since the LSI is an index of calcium carbonate saturation. Five other factors affect this saturation:

  1. pH
  2. Carbonate Alkalinity
  3. Water Temperature
  4. Total Dissolved Solids (TDS)
  5. Cyanuric Acid (CYA)

But primarily, calcium is the rock to build your LSI pool chemistry castle upon. Give the pool the calcium it needs, and by and large, it will not have to seek calcium on its own.

Core belief #3: Timing matters

The National Plasterers Council offers startup courses that are very informative. In the startup technician course, you will learn the in-depth chemistry of plaster surfaces and how they behave in the field. One thing that stood out when we took the course was how much time it takes plaster to cure.

The most vulnerable time for plaster is the first 60 days, which is when the bulk of its curing happens. Part of curing cement is a process called hydration, when Calcium Oxide (CaO) in Portland Cement is hydrated (H2O). This reaction yields Calcium Hydroxide, Ca(OH)2. In a perfect world, no calcium leaves the cement. But in a pool with aggressive water filling it? Calcium hydroxide is the first thing to be stolen from the cement in the plaster. It’s being stolen to feed the water the calcium it craves (see Core belief #2 above).

So timing matters. The sooner we can give water the calcium it craves, the less calcium it will steal from the curing plaster. To prevent plaster dust, balance the LSI as soon as possible. Some have proven this can be done using high levels of sodium bicarb on startup, and we have proven it can be done using calcium on startup. Do what works best for you, and you can use our free LSI Calculator App to dose it properly.

The undeniable importance of calcium hardness

Putting our three core beliefs into practice is simply a matter of testing tap water for all the LSI factors. Then, using our LSI Calculator App, figure out how much calcium and sodium bicarbonate you will need for the pool. Add calcium first by pre-dissolving it in buckets (to let the heat off). Get it in the water as soon as you can. Bucket by bucket, continue to add it.  Some people even use large trashcans and siphon calcium-rich water into the bottom of the pool as its filling. Again, find what works for you.

naturally free scale and metal sequest

So we told our customer to get their pool up to 300ppm calcium ASAP, and to use our startup chelant, Naturally FREE. They followed our recommendations and were thrilled to find out they had no need to brush plaster dust…because there wasn’t any.

You can do the same. If you need help with the startup, contact us. Thanks for your time.

Organic vs. Inorganic Phosphates | re-post

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Inorganic phosphates and organic phosphates can get confusing. This is a re-post from an article on Orenda’s website. It pertains to our audience too, so we thought we would share it, and give credit where credit is due. The original article can be found here.

Different types of phosphates

Did you know there are many different types of phosphates? In the water treatment business, most of us use “phosphates” as a general term to describe them all…but sometimes that can be misleading. There are so many types of phosphates and they react differently.

Let’s start by dividing all types of phosphates into two main categories: organic phosphates, and inorganic phosphates.

Organic Phosphates (Organophosphates)

Organic phosphates are esters of phosphoric acid, also known as orthophosphoric acid (H3PO4). Okay…so what are esters? An ester is what you get when an organic substance (usually a hydrocarbon or alkyl) replaces a hydrogen atom in an acid. This swap (Hydrogen for an organic hydrocarbon or alkyl) makes the substance change from inorganic to organic.

Those of us who are not organic chemistry experts refer to esters as fats and oils. Natural fats and essential oils (like Omega 3) are esters of fatty acids.

According to the National Institute of Environmental Health Sciences (a division of NIH), organophosphates are a key ingredient in about half of known pesticides and nerve agents. To be clear and distinguish this from the previous statement, we are now talking about organic phosphates specifically…not other esters (fats).

Click here to see examples of organic phosphates. Fortunately, organic phosphates are not common in swimming pools.

Inorganic Phosphates

Now let’s get to the more common phosphates that we deal with in the water treatment business: inorganic phosphates.

“In biological systems, phosphorus is found as a free phosphate ion in solution and is called inorganic phosphate, to distinguish it from phosphates bound in various phosphate esters. Inorganic phosphate is generally denoted Pi and at physiological (neutral) pH primarily consists of a mixture of HPO2-4 and H2PO4 ions.” – PubChem CID 1061

We can divide inorganic phosphates into two categories: orthophosphates and condensed phosphates.


Orthophosphates are also called reactive phosphates. They are the most common in water treatment situations, as they directly contribute to the eutrophication of a body of water. Orthophosphates are found naturally in the environment and in water but are also artificially added to fertilizers.

In swimming pools, orthophosphates are the most prevalent of all types of phosphates. These are the ones that eutrophy water (meaning they are an essential nutrient for plant growth…specifically algae). Usually, when people in the water treatment business talk about phosphates, they are referring to orthophosphates.

Orthophosphates do not directly interact with chlorine. They cannot be oxidized. The only ways they can be removed is with a phosphate remover product or with reverse osmosis filtration (R.O.).

Click here to see examples of orthophosphates. You’ll notice a substance called phosphonic acid. Phosphonic acid is commonly used in drinking water treatment as a sequestering agent for metals and minerals (like calcium). Phosphonic acid is also used in pool chemicals used for stain and scale removal/prevention.

Condensed phosphates

Condensed phosphates are types of phosphates that contain salts, metals or minerals like calcium. Within this category are pyrophosphate, metaphosphate, and polyphosphate. Calcium phosphate (Ca(H2PO4)2) is a good example of a condensed phosphate. These types of phosphates are naturally occurring, but can also be synthetically combined to be used in various industries.

For the example of calcium phosphate, our bones and tooth enamel are strengthened by it. In swimming pools, calcium phosphate can harden sand and regenerative DE filter media like concrete. It can take a jackhammer to crack through it.


There are too many variations of phosphates to write about. It seems like any combination of P, O, H and numbers, + and – signs can be a type of phosphate. Given that we are not chemists, it gets daunting. We know. Hopefully, this article has simplified the chemistry so it is easier to understand.

As it pertains to water treatment, orthophosphates are the primary type we encounter. We recommend removing phosphates to keep them below 500 ppb (µg/L) for easier, proactive water treatment. If you do come across organophosphates or condensed phosphates, they could give you more trouble.

Six Factors that weaken chlorine in swimming pools

weaken chlorine, OCl-, hypochlorite, pool chemistry, hypochlorous acid, HOCl vs. OCl-, phosphates, alkaline pH, pool pH

Slow Chlorine = Weak Chlorine

Sanitization and disinfection are the two primary responsibilities of chlorine. Chlorine’s secondary responsibility–or, more accurately, it’s secondary obligation–is oxidation. In terms of residual sanitizer out in the pool water, chlorine is the first line of defense against common recreational water diseases like pseudomonas aeruginosa; bacteria like e. coli; other germs like staphylococcus aureus and giardia; and living organisms like algae.

So its speed is critical.

If chlorine is slowed down, its kill times, referred to in biochemistry as contact time (CT) are proportionally increased. And that’s not a good thing when it comes to keeping water safe. We want chlorine to kill germs and viruses fast and efficiently. Slow chlorine is weak chlorine, and there are several factors discussed in this article that drag chlorine down.

To help protect people against those nasty waterborne pathogens, there are secondary disinfection systems like UV, but they are a point-of-contact system.  In other words, secondary disinfection systems can only affect what they touch, and they only touch what passes through them. Chlorine, on the other hand, is flowing with the water throughout the entire pool and system…it’s everywhere. So let’s get into what slows it down.

Factors that slow chlorine

1. Metals

When chlorine is introduced to the water, it reacts first with metals like iron and manganese. Chlorine oxidizes these metals first and foremost, which in turn knocks out available chlorine early on. The reaction looks like this:

Cl+ Fe † FeCl2

You can see this on the chart below. Notice that chlorine residual does not present itself until point A. What happened prior to that? Why did it not start building residual from the start?  The answer is metals between 0 and point A. The chart labels it as “Destruction of chlorine residual by reducing compounds.” For more information on the science of breakpoint chlorination, read this.

breakpoint chlorination, hyperchlorination, superchlorination, chlorine pool, metals wipe out chlorine

2. Non-living organics (bather waste)

Why are we depending on chlorine alone to remove non-living organic waste from the pool? Chlorine is critical to the safety and wellbeing of everyone in the pool because of disinfection…not removing bather waste. But alas, the bather waste (such as sweat, urine, body oils, mucus, lotions, cosmetics, deodorants and hair gels) must be oxidized to get them out. Right?

Wrong. Oxidation is not the most efficient or effective means of removing bather waste from a swimming pool. Try using SimplyPURE enzymes instead. They are strong enough for wastewater; yet safe enough to meet the NSF/ANSI 50 standard. The enzymes flow throughout the entire pool system–alongside chlorine–and devour organic contamination to reduce the burden on chlorine. By using enzymes, chlorine is freed up to sanitize and disinfect…and that’s what we need it for in a pool.

More specifically than non-living organics, however, are nitrogen compounds. Nitrogen compounds combine with chlorine (to create combined chlorine). The breakpoint chlorination process shows this occurring, then the eventual destruction of combined chlorine compounds like monochloramine and dichloramine. Eventually, with enough hypochlorous acid (HOCl) to break it down and convert it to nitrogen trichloride (aka trichloramine), these compounds will off-gas into the air. They then become an air quality problem.

3. Direct sunlight (UV)

free chlorine, sunlight chlorine, chlorine in direct sunlight, chlorine and UV, UV breaks down chlorine, sunlight weakens chlorine, sunlight destroys chlorine

Direct sunlight breaks down chlorine. Without a stabilizer (cyanuric acid) in the water, as much as 90% of free available chlorine could be destroyed within just two or three hours.

We conducted fairly diligent research for this article. We found plenty of sources indicating that direct sunlight breaks down chlorine and bromine; a fact that is irrefutable. What we were looking for, however, we have not yet found. Does anyone know if UV sanitation systems for pools also break down chlorine? And if so, how much? Is it similar or even more severe than sunlight? We think it must be less severe than sunlight, but we honestly do not know. It would be great if a UV manufacturer could contact us and let us know.

But back to what we know. Direct sunlight breaks down chlorine in a matter of hours. Obviously, broken down chlorine is ineffective at sanitation, so therefore sunlight makes this list. Fortunately for outdoor pools, several decades ago a wonderful discovery was made, called…

4. Cyanuric Acid (chlorine stabilizer) Overstabilization

cyanuric acid, CYA, weaken chlorine, CYA lower ORP, CYA and ORP

The more stabilizer you have in your pool, the slower the chlorine.

Without cyanuric acid (CYA), chlorine would break down in a matter of hours in direct sunlight. Something about the UV rays breaking apart the HOCl and OCl- itself, but the specific chemistry is not important to this conversation. Just know that without cyanuric acid, also known as chlorine stabilizer, outdoor pools need to be constantly replenishing free chlorine. It’s good to have some stabilizer in an outdoor pool.

The key is moderation. Overstabilization is the problem to avoid, and it’s all about the free chlorine to cyanuric acid ratio (FAC:CYA), which we will discuss in a moment. The US Centers for Disease Control (CDC) released a mandate for regulating the use of cyanuric acid in commercial swimming pools. The new regulation stipulates CYA levels cannot exceed just 15 parts per million! That can be a real problem for pools that use trichlor.

CYA’s dramatic impact on chlorine kill rates

Why limit the use of a stabilizer that protects chlorine from sunlight? Because it also weakens chlorine. Pool industry experts disagree and debate whether or not “chlorine lock up” is a real thing. The notion being that CYA prevents a certain amount of chlorine from being used. The numbers we have heard range between 5-10%, but the best article we have found on the topic of chlorine lock is from Service Industry News. Read the article. It’s worth your time. And we quote:

“Richard Falk derived his ratio in part by recognizing that even if the free chlorine is the same, the concentration of hypochlorous acid (effective chlorine) changes when cyanuric acid is introduced at different levels…

…He did this by recognizing hypochlorous acid, HOCl (the killing form of chlorine) is proportional to the ratio of free chlorine to cyanuric acid:


Beginning with Powell’s best guesses on free chlorine values that are effective for a given cyanuric acid concentration, Falk determined that one should have a minimum free chlorine to cyanuric acid ratio of 7.5 percent to prevent algae in traditionally chlorinated pools.

Falk’s ratio has made doing the math to prevent algae incredibly easy.

FC = 7.5% x CYA

For example, if the measured cyanuric acid in a swimming pool is 30, then a pool operator should maintain a minimum free chlorine level of 2.25 ppm.

2.25 ppm FC = 7.5% x 30 ppm CYA

If the cyanuric acid is at 70 ppm, the free chlorine should be maintained at a minimum of 5.25 ppm.

5.25 ppm FC = 7.5% X 70 ppm CYA

So, assuming Falk’s numbers are correct, the factor of 7.5% is an important one to understand. If your pool has 100ppm cyanuric acid, you basically don’t have free chlorine until you exceed 7.5ppm chlorine. That’s your new baseline. Crazy, right?

5. High pH

pH and chlorine, high pH can weaken chlorine, weak chlorine, alkaline pool water, chlorine efficiency, pool chemistry

In non-stabilized water (meaning no CYA), The higher the pH, the lower the concentration of HOCl in free chlorine readings. The weaker form of chlorine, hypochlorite ion (OCl-) increases and surpasses HOCl around 7.5 pH.

As you can see from the chart above, pH has a direct impact on the dissociation of H+ from hypochlorous acid in the pool. Hypochlorous acid (HOCl) is the strong, killing form of chlorine We need it in the water! The higher the pH, the less of it there is, as it is replaced by the weaker chlorine, the hypochlorite ion (OCl-). So yes, more alkaline pH can weaken chlorine. Conversely, the lower the pH, the stronger the chlorine, because it has a higher percentage of the strong HOCl.

Let’s be clear about something that sounds somewhat contrarian to industry textbooks and the chart above. The pH of your water dictates HOCl concentrations in pools with no cyanuric acid (CYA). With CYA present, the impact pH has on HOCl concentrations is very little, if not negligible. See the chart below that puts the previous chart in context.

cyanuric acid, CYA, HOCl, pH does not control chlorine strength, pH and HOCl, pH chlorine strength

Notice the red line (HOCl concentration) plummets in the presence of CYA. pH now has a negligible impact on HOCl concentration, and chlorine speed/strength is now dictated by CYA. The new blue line at the top of the right graph represents chlorine bound to CYA, also called isocyanurates.

6. Phosphates

pool sanitization, phosphates, pool phosphates, kill rate versus growth rate, preventing algae, green poolYes, phosphates indirectly impact chlorine too. Phosphates are an essential micronutrient for organisms to reproduce and grow. In particular, algae. Reproducing algae consumes more and more chlorine in the sanitization battle between the sanitizer and contaminants.

Phosphates are an invisible problem in swimming pools that brings about many consequences. And since chlorine cannot simply oxidize phosphates out of the water, they need to be removed by a dedicated phosphate remover like Blue PRO. Phosphate levels over 500 ppb fuel the reproduction of algae, provided other conditions are met. And while removing phosphates does not kill algae, it can certainly slow its reproduction rate, allowing the sanitizer (chlorine) to stay ahead in the battle, preventing outbreaks.

Phosphates: The invisible problem in swimming pools

phosphates in pool water

Orthophosphates come from phosphorus, a naturally occurring element found in soil.

Phosphates are an invisible problem in swimming pools. Phosphorus, the naturally occurring element, comes in many forms…but as it pertains to pools, we care about orthophosphates. Phosphates in swimming pools have become a prevalent problem, as evidenced by the growing amount of phosphate removers sold in the U.S. pool market. But why are phosphates a problem?

First, we need to understand what phosphates are. Don’t worry, we’ve got you covered. Our parent brand–Orenda–has an article about it. Phosphorus is a key ingredient in fertilizers and is naturally occurring in the environment, yadda-yadda-yadda. Here’s the point: phosphates are an invisible problem particularly in swimming pools because of what they indirectly do to chlorine efficiency. And perhaps more importantly, because chlorine cannot remove phosphates on its own.

Kill Rate vs. Growth Rate

pool sanitization, phosphates, pool phosphates, kill rate versus growth rate, preventing algae, green poolSanitization is essentially a match between the killing rate of the sanitizer (usually chlorine) vs. the growth and reproduction rate of a given contaminant. All living organisms–including microorganisms–need phosphates to build new cells and grow.

As long as the kill rate stays ahead of the growth rate of say, algae, there will be no outbreak. But if the growth rate meets or exceeds the sanitizer’s rate of kill, an outbreak is the result. This is when pools turn green.

The conditions necessary for an algae outbreak include weakened or low levels of free available chlorine (FAC), and/or an abundance of micronutrients like phosphates. An abundance of micronutrients creates a condition in water called eutrophicationEutrophication is when there are so many nutrients that algae can take over a body of water and starve out other organisms…either by blocking their sunlight, or simply by dominating the ecosystem. Here’s a photo of Lake Erie’s algae bloom in the summer time:

lake erie algae bloom, eutrophication, phosphate, orthophosphates, phosphate remover, algae prevention, types of phosphates

The sanitization battle needs to be won. Swimming pool health and safety depend on it. So there are two sides of the battle that can be worked on.

Boost the Kill Rate

We should do everything within reason to optimize chlorine efficiency and its killing speed. We need to get rid of as many factors that weaken chlorine as possible. We strongly recommend supplementing chlorine to handle bather waste, either with a secondary system like UV or Ozone, or with enzymes to break down and digest non-living organics.

Another important item is keeping CYA to a minimum, and preventing overstabilization. CYA dramatically slows chlorine’s kill times when the ratio of CYA to FAC gets too high. Studies show the optimal CYA levels for outdoor pools to be between 15 – 30 ppm, but going as high as 50 is acceptable too, provided you have enough FAC to maintain a decent ratio.

Slow the Growth Rate

On the other side of the battle, we can slow the growth rate by reducing phosphates. There are three main nutrients that algae needs to thrive: carbon dioxide, nitrogen, and phosphorus. CO2 is essential to pH balance, and it will be everpresent in water, so we cannot really remove it without consequences. Nitrogen will be oxidized by chlorine through the process of breakpoint chlorination, and eventually reduced down to nitrates. Nitrates cannot be further oxidized, so they are really only removed by draining water out of the pool. So that leaves us with phosphates.

Phosphates are easy and safe to remove, using BluePRO phosphate remover. It reacts on contact with phosphates, which will turn into a white cloud for a few hours (or more). When the reaction is complete, a crystalized phosphate falls out of solution to be either filtered or vacuumed out of the pool. Removing phosphates regularly helps keep the residual levels low. According to most credible sources on this topic, the goal should be to keep phosphates below 500 parts per billion (ppb).

How to phosphates get into swimming pools?

Phosphates are in our drinking water

We were filling a summer pool in Michigan that was about 300,000 gallons. Before the pool was even completely full, we tested for phosphates, and it was about 1500-2000 ppb. Since the goal is to stay below 500 ppb, we added Blue PRO, and the water clouded immediately.

Blue PRO, phosphate removerBut the question arose, “How can there be phosphates in the water? It’s literally filling up right now.” The answer is simple: the phosphates are in the tap water.

Yes, you read that correctly. See, municipalities often put phosphonic acid in their water sources because it’s used as a sequest for minerals and metals. Phosphonic acid helps protect the pipes from scale and corrosion.

Sequestering agents are often phosphate-based

Phosphonic acid products are very common in the pool market too, used as stain removers and scale prevention products. Fortunately for you, our Naturally FREE stain and scale inhibitor is not phosphate based. In fact it doesn’t even contain phosphates at all. But we digress. Just be aware that most metal removers and stain prevention products are actually phosphate-based products. And they usually will not show up on an orthophosphate test kit at first, because they are some sort of polyphosphate or condensed phosphate. But rest assured, in direct sunlight and an oxidizer like chlorine, they will break down into orthophosphates.

Phosphates are everywhere in nature…including us

Finally there is the natural introduction of phosphates from nature, and from people. When it rains, debris like pollen, leaves, pine needles, grass clippings, and soil can find their way into an outdoor pool. For indoor pools, people themselves produce phosphates that end up in the water as well. Just ask any commercial pool with a busy swim team that trains hard and sweats.

Phosphate Myths

People talk a lot about phosphates in the pool business nowadays, particularly as they pertain to algae. Yes, phosphates are a food source for algae (though not the only one), but removing phosphates does not directly kill algae. In fact, none of our products kill algae, or anything else for that matter. That’s not what Natural Pool Products do.

Phosphates also do not attack chlorine, or vice versa. This is actually part of the issue…chlorine has no way of getting rid of them. That’s why a phosphate remover like Blue PRO is necessary.

By removing phosphates, the water simply has less nutrients for algae to grow in the first place…but it can still happen in some cases. Also, if you currently have algae, using a phosphate remover may not be as effective as you hope, because algae actually stores phosphorus in its cell walls. So it needs to be killed before that phosphorus can be removed from the water.

We hope this article helps you better understand phosphates in pool water.

Introducing Natural Pool Products

Our line of natural pool products simply perform

Have you ever bought a pool chemical that worked (at least to some degree), but maybe wasn’t quite strong enough to get the job done? Or maybe last year it worked, and this year it seems weaker? Perhaps you have a pool that needs a deep clean, but given your time frame and the products available on the market, your hands are tied.

Nobody likes over-promising or under-delivering companies. So we made darn sure we’re not one of them. Natural Pool Products is a brand that simply performs. The products do what we say they do, and they will never be watered down.

“Just do what you say you’re going to do, when you say you’re going to do it.”

Being successful in the pool business–or any business, for that matter–means building trust with customers, vendors, and everyone else in your sphere of influence. People struggle to build trust when they don’t follow through with their promises and deliver results. We live by a simple rule: just do what you say you’re going to do, when you say you’re going to do it.

Natural Pool Products: Simplify pool care

Look at our line of products. You will find our product line is narrow and focused; every product has a purpose. Rather than spit out dozens of product variations, we instead keep our line simple, and allow pool operators and service pros to integrate them into their regimen. Let’s not complicate pool care…instead, let’s streamline it.

Think of all the chemicals it takes to just adjust pH and alkalinity in a swimming pool. Combined with chlorine consumption and backwashing waste, it’s an inefficient system. And yet, it’s the traditional way to manage pool chemistry. Our best customers are the ones who have long believed in the traditional way of doing things…but strived for more. They sought better water quality, better clarity, less chemical use and of course, better margins.

Are you happy with how your pools are managed now? If there were a better way; a more meaningful water chemistry program with less, would you try it? If so, welcome to Natural Pool Products. We’re glad you’re here.