The CDC’s Model Aquatic Health Code (MAHC) Update

The CDC’s Model Aquatic Health Code (MAHC) has been updated

“New: Specifies that numerous pool chemicals (stabilizers, pool-grade salt, clarifiers, flocculants, defoamers, and pH adjustment chemicals) must meet either NSF/ANSI Standard 50 or NSF/ANSI Standard 60, and/or have a U.S. EPA FIFRA registration. (5.7.3)”

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nsf international, Orenda chemicals, NSF/ANSI-50, NSF Standard 50, NSF Standard 60, NSF certificationSpecifically, the code states that treatment chemicals must be certified, listed and labeled to either NSF/ANSI 50 or NSF/ANSI 60 by an ANSI-accredited certification organization, and/or have a U.S. EPA FIFRA (the Federal Insecticide, Fungicide, and Rodenticide Act) registration and be used only in accordance with the manufacturer’s instructions.”

This is a big deal for the health and safety of commercial swimming pools.

What is the MAHC? And what is NSF?

The Model Aquatic Health Code (MAHC) is a set of recommended standards and guidelines for the aquatics industry from the U.S. Centers for Disease Control (CDC). The MAHC is a code that can be adopted in whole or part by state or local governments, and is designed to help guide local governments in creating aquatics codes to prevent health and safety-related problems in recreational water.

The NSF, on the other hand, is a global independent organization that writes standards, tests and certifies products for the water, food, health sciences and consumer goods industries. NSF International has a committee of manufacturers, designers, scientists and other subject-matter experts who vote on what the standards should be, then the NSF goes out and tests products to see whether or not they comply with those agreed-upon standards. The MAHC just recognized that NSF-50 is a standard worth meeting to be considered safe for commercial pools.

Why have standards for pool chemicals?

Without a credible, neutral third party like NSF evaluating products for quality and safety, manufacturers could sell almost anything. For swimming pools, bathers are exposed to pool chemicals not only by accidental ingestion (swallowing some pool water), but absorption through skin. Human exposure to pool chemicals is a health and safety issue, and the MAHC recognizes that.

Our food is regulated by the FDA, and manufacturers are required to put a table of ingredients, nutritional facts and allergen information on packaging. Household chemicals are regulated by the EPA, and are required to put such certifications on their labels. The CDC is now specifying commercial swimming pool chemicals need to be held to a similar standard of quality and safety.

There are three types of certification mentioned in the new MAHC update:

Swimming pool chemicals being used in commercial pools must have at least one of those certifications. Let’s briefly cover each of these standards.

NSF/ANSI Standard 50

NSF-50 is the recreational water safety standard for equipment and chemicals. Like other standards from NSF International, the standards are created and voted on by manufacturers and experts in the industry. The NSF then tests products with intense scrutiny to see if the products meet the standard. The registered trademark NSF® mark is then put on the label of such products that meet the standard.

If a product with the NSF® mark is tested by the NSF, and it fails to meet the standard, the manufacturer is liable for penalties and can lose the NSF certification. For swimming pool chemicals, an example of this could be changing the chemical formula without telling NSF, and having the new formula tested and certified. Perhaps it could be watered down to a point where it no longer works like it is supposed to, or a harmful additive is blended in.

NSF International is a widely accepted organization that provides independent testing. It’s credibility is now recognized by the CDC. So much so, that it is on par with the EPA.

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Every single Orenda product meets NSF/ANSI Standard 50.

NSF/ANSI Standard 60

NSF-60 is the drinking water safety standard for equipment and chemicals. Compared to NSF-50, NSF-60 is a more rigorous health and safety standard to meet, given that it’s for drinking water. Any chemicals or equipment used to treat drinking water must meet the NSF-60 standard. Calcium Hypochlorite is one example of a pool chemical also treats drinking water, and depending on the brand, cal hypo may already be certified to NSF-60.

Orenda’s enzyme products (CV-600/700CE-ClarifierCE-SpaSPA-500) meet NSF/ANSI Standard 60.

EPA FIFRA Registration

Any product that claims it can kill/sanitize/disinfect anything, it must be registered with the US Environmental Protection Agency (EPA). This is required under the US Federal Insecticide, Fungicide and Rodenticide Act (FIFRA). EPA Registration is not required for speciality chemicals that do not make such claims. Products such as phosphate removers, enzymes, clarifiers, flocculants and pH adjustment chemicals do not claim to kill anything, so the EPA does not need to be involved.

If you notice, on the label of algaecide and chlorine products, there is an EPA registration number printed on it. Without that printed registration number, no ‘killing claims’ can be made.

No Orenda products have (or need) EPA FIFRA Registrations, because Orenda does not manufacture any sanitizing chemicals. We have no algaecides or any product that kills anything.


In commercial swimming pools, the MAHC now specifies pool treatment chemicals must be NSF/ANSI 50 or 60 certified (or EPA Registered) and appropriately labeled as such. This MAHC update encourages non-certified chemicals to either get certified, or stay out of recreational water. As we said at the beginning, this is a big deal for the health and safety of swimming pools.

Every Orenda Product is, always has been, and always will be certified to a minimum of NSF/ANSI Standard 50. To us, it’s the right thing to do, and we are pleased that the MAHC has officially recognized the importance of setting health and safety standards for pool chemicals.

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Does My Pool Guy Need A Contractor’s License?

Guest Author: Originally published August 12, 2016 by Javier Payan

In the State of California, a contractor’s license, which is issued by the California State Licensing Board or CSLB, a contractor’s license is not required to clean pools. The reason for this is that, in California, a contractors license is required if a job or project costs $500.00 or more. So as long as your pool guy is not charging you $500.00 or more to clean your pool, a license is not required. Now, if that same pool guy installs new equipment or does repairs that exceed $500.00, then a license is required by the CSLB In my experience most pool guys do equipment repairs and or equipment installation, therefore they should be licensed.

The CSLB is under the Department of Consumer Affairs, the consumer agency which regulates business in California. This is the part of the state government that is looking out for the consumer.


Do you know who is in your back yard? If they have a contractor’s license, they have been background checked.

What is required to obtain a pool contractor’s license?

So should your pool guy have a contractor’s license? I would always say yes, even if he/she does not do jobs over $500.00. My reasoning is this: in order for a contractor or business to obtain a license from the CSLB,

1) an application needs to be submitted and approved,

2) a test that covers basic business law and another test that covers the contractor’s related trade must be passed,

3) a fee has to be paid to the CSLB,

4) each contractor has to submit fingerprints to be kept on file with the CSLB,

5) a background check needs to be passed,

6) no outstanding debts such as child support or spousal support must come up,

7) a criminal background check must be passed, etc.

Benefits of a background check

Sounds like a lot of hoops to have to jump through. However, when you deal with a licensed contractor, all these items must have had to be met.

Remember, all this is the efforts of the Department of Consumer Affairs trying to help the public screen people who will enter your home or property to do business with you.

Lets ask the question again. Does my pool guy need to have a contractor’s license? No, but he really should. Without one, you really do not know who you are allowing onto your property. You can look up the licensing status of each contractor on the CLSB website,

About the Author: Javier Payan owns Payan Pool Service in San Diego, CA. He and his team manage hundreds of residential pools and insist upon doing things the right way. Javier knows that with his contractor’s license, he is doing everything legally and ethically, paying taxes and keeping records. Unlicensed workers may not be. Here’s a video of us sitting down with Javier for a Customer Spotlight.

Three Types Of Calcium Dust In Swimming Pools

There are three distinct forms of calcium carbonate that we commonly find in swimming pools. They are carbonate scalecalcium crystals [calcite]and the topic of today’s article, calcium dust.

Our topic today ties into our core message at Orenda about the Langelier Saturation Index (LSI). Remember, the LSI is a measurement of the saturation of calcium in water…specifically the saturation of calcium carbonate.

Low-LSI water seeks more calcium, and therefore dissolves calcium wherever it can be found. For a gunite pool with a cementitious surface (like plaster, pebble, quartz, etc.), the most readily available source of calcium is pretty obvious…it’s the surface. For vinyl liner and fiberglass pools, the sources of calcium may not be there at all, which is why these surfaces can get faded and damaged by aggressive water. The water is starving for calcium.

On the opposite end of the spectrum, high-LSI water has too much calcium carbonate, and deposits it out in the form of carbonate scale. Scale tends to deposit in the hottest places first: like a pool heater, salt generator, and a pretty water feature or tile line that gets a lot of hot sunlight all day.

Is calcium dust the same as calcium scale?

Now that we have reviewed the LSI, let’s talk about calcium dust. Calcium dust is precipitated calcium carbonate, just like carbonate scale, but they are not the same thing. Calcium dust comes from a different place, with different chemistry involved. Calcium dust can be formed in a few different ways.

Plaster Dust

The most common form is called plaster dust, where low-LSI tap water fills a newly plastered pool and begins dissolving calcium in the cement. Within the cement, the most soluble form of calcium is called calcium hydroxide, Ca(OH)2. Calcium hydroxide has a pH of about 12.6-12.8, which is really high. When brought into solution, it rapidly changes the pH of the water near the surface, which dramatically raises the LSI in that immediate area.

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Once dissolved, carbonate ions and/or carbon dioxide in the water react with the calcium hydroxide and carbonate it. The reaction creates calcium carbonate, which is not soluble in water. The calcium carbonate precipitates out in the form of dust. This dust is known as plaster dust, because it has been viewed as an inevitable part of starting up a pool.

In reality, plaster dust is not inevitable, if you follow the right startup procedure. By adding the right amount of calcium or sodium bicarbonate as the pool is filling up, plaster dust can be prevented before it starts. Watch the video below to witness it for yourself.

Plaster dust is hard evidence that valuable calcium is being stolen from the cement in the surface; cement still trying to hydrate and cure. Haven’t you noticed how calcium tends to “drift up” during startup, and the pH spikes high for the first several days you come back to the pool? These things happen because the pool water is stealing high-pH calcium hydroxide from the new plaster finish. Why? Because if you do not balance the water according to the LSI, the water will find LSI balance on its own–at the expense of your brand new surface.

Winter Dust

calcium dust, orenda pool, calcium dusting, plaster dust, winter dust, calcium carbonate in pools, calcium precipitateLet’s say you winterize a pool, and come back in the spring time to open it. Have you ever seen dust in your pool, or perhaps what you think is “scale” at the bottom of the pool? This calcium may be stuck on your plastic fittings too. This is very similar to plaster dust, except the plaster already cured. This sort of dust can occur with surfaces many years old, and seems to only occur in very cold water (40ºF or colder in the winter).

You will see small white rings around aggregate in with this condition, which indicates the loss of–you guessed it–calcium hydroxide. The rings occur because this calcium hydroxide is most often found in the interfacial transition zones (ITZs) between aggregate. Rings around aggregate mean the ITZs lost material.

This high pH calcium hydroxide spikes the pH of the pool, and eventually the water stops eating the walls because the pH provides temporary LSI equilibrium through the winter. But unlike plaster dust, the precipitation of calcium carbonate does not happen immediately. Rather, the dusting is delayed, and we think this happens because of warming water temperature.

We think the precipitation occurs as the water goes from freezing to say, 60ºF by the time you get there in the spring.  The water already stole the calcium hydroxide and spiked the pH, and high pH in warmer water begins to precipitate calcium carbonate as dust.

For some reason, this form of calcium dust is often mistaken for carbonate scale. This dust formed for a different reason, but technically, as the water warmed up, the LSI changed and precipitated calcium carbonate out of solution. So sure, if you want to call it scale, you can, but we advise against it. Why? Because semantics matter: horrible habits have developed in cold climates, like trying to keep calcium low going into the winter, as to prevent scale. Rule of thumb: if you see it on the bottom of your pool, it wasn’t a high-LSI problem like scale. It was a low-LSI problem.

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Calcium dusting over the winter. This dust slowly precipitated as the water warmed up.

Carbonate Clouding

soda ash cloud, cloud pool, soda ash clouds a pool, orenda soda ash, orenda poolA third type of calcium dust is created when adding chemicals improperly. One way is when you add soda ash, either too fast or too much. This drives the pH in its immediate area up, which converts bicarbonate ions to carbonate ions, which then attract calcium and create calcium carbonate. Calcium has a strong attraction to carbonate.

This is why pools sometimes cloud up when throwing soda ash in. Here again, we recommend pre-dissolving chemicals before adding them to a pool, not just throwing dry chemicals in. And this sort of clouding is not only caused by soda ash. Have you ever tried adding calcium chloride to the pool at the same time as sodium bicarbonate?  It clouds up with a similar reaction.

How to prevent calcium dust

The point of this article is to describe three distinct forms of calcium dust: plaster dust, winter dust, and carbonate clouding. We made up the terms ‘winter dust’ and ‘carbonate clouding’ because we have been looking for terms in the industry to describe these two phenomena, and have not yet found any. These forms of dust happen for different reasons, and prevention is easier than remediation.

Sure, acid will dissolve any and all of these forms of calcium carbonate, but it matters how the dust got there in the first place. Once you know that, use the Orenda LSI app to figure out the proper correction strategy before the problem starts. Do your part with the LSI in preparation for changing temperature or other conditions, and SC-1000 can help you do the rest. If you need help, we would love to hear from you.