drpool-chlorine-levelsWelcome back class to another home-school edition of pool school. I got a question in the email this week; “Dr. Pool, how do I know if my pool water is safe from the Coronavirus?”

Before we go too deep, let me say first-off, if your pool looks blue and clear, and you have tested for good water balance and a normal (2-4 ppm) Free Available Chlorine level, your swimmers are most likely safe from pathogens, like bacteria and viruses.

According to this CDC document; “There is no evidence that COVID-19 can be spread to humans through the use of pools and hot tubs. Proper operation, maintenance, and disinfection (e.g., with chlorine and bromine) of pools and hot tubs should remove or inactivate the virus that causes COVID-19.” – Centers for Disease Control, March 10, 2020.

Many of our customers however, have increased chlorine levels in the pool, and are shocking the pool more frequently. We know this because sales for In The Swim chlorine have risen sharply in the last 30-days. Also more of you are choosing to stay at home (good idea), and buy pool supplies online this year (great idea).

Swimming Pool Sanitizers

A sanitizer is a chemical that will kill germs (bacteria, viruses, fungi and parasites) that could make you sick. Also defined as a chemical or process that will kill or deactivate 99.9% of bacteria on a surface or in a body of water.

Chlorine tablets and sticks are used to keep algae, bacteria, parasites and viruses from growing. You need a constant and consistent level of Free Available Chlorine in the pool, with a recommended pH level. The CDC recommends pH 7.2–7.8 and a Free Available Chlorine concentration of at least 1 ppm in pools and at least 3 ppm in hot tubs/spas.

In addition to a good pH (and Total Alkalinity) levels in the pool, to give chlorine the highest levels of efficacy (potency), don’t let the bright sun deplete chlorine levels during the day. The  Model Aquatic Health Code, or MAHC recommends a 30-50 ppm level of cyanuric acid, better known as pool conditioner or chlorine stabilizer. This minimum chlorine residual should be higher (2.0 ppm pools / 3.0 ppm spas), if the Cyanuric Acid level is higher than 50 ppm.

Biguanides are pool treatments such as Baquacil, Revacil or Aqua Silk, which are a class of sanitizer that do not contain chlorine, but rely on long-chain polymers as both sanitizer and antiseptic, and in higher concentrations, as a disinfectant.

Mineral Sanitizers, such as those created by Nature 2 and Frog, use the bactericidal properties of silver and copper ions to reduce contaminant levels, making the job easier for your main chlorine sanitizer.

Swimming Pool Oxidizers

An oxidizer is a chemical that steals an electron from another compound, thereby reducing the contaminant into their base components, and in the process, destroying them. An oxidizer is used to destroy organic contaminants, while a sanitizer is used to destroy pathogens such as bacteria and viruses that can make you sick.

Chlorine is both a sanitizer at low levels and an oxidizer at higher levels. For swimming pools, chlorine tablets, as the primary sanitizer, are the cheapest and most convenient way to add a consistent level of chlorine to the pool, all through the day, without creating peaks and valleys of chlorination.

Pool Shock however, is designed to dissolve rapidly and raise the chlorine level in the pool very high and very fast, to destroy organic and pathogenic contaminants. It’s called ‘Pool Shock’ because the chemical rips through the water very fast, like an electric shock. Available in 65% strength (Pool Shock), 73% strength (Super Pool Shock), and stabilized (Di-Zap).

Hydrogen Peroxide is another oxidizer that will steal your outer electrons when you’re not looking! A concentrated version of that used for swimmer’s ear and to dye hair platinum blonde, Hydrogen Peroxide also makes a great pool oxidizer when used with biguanide sanitizers such as Aqua Silk, for a complete sanitizer/oxidizer pool care system, as an alternative to tablets/shock. With this system, an algaecide is also used. Note: Do NOT use hydrogen peroxide in a chlorine pool, as it will remove the chlorine.

Non-Chlorine Shock is a class of potassium salts, sometimes referred to as MPS or as (potassium) monopersulfate, that is a granular chlorine-free oxidizer for pools and spas. Very effective as an oxidizer, but it does not raise the Free Available Chlorine level, or kill algae, and is not EPA registered as a sanitizer.

Swimming Pool Disinfectants

Whereas a sanitizer will kill 99.9% of bacteria strains, disinfected means a complete kill of 99.999% of pathogenic germs, including viruses, mold, bacteria and more. Disinfected surfaces or pools have been shocked very heavily, to destroy 100% of contaminants. The difference between sanitation and disinfection is the time it takes to achieve each level.

Consider Super-Chlorinating vs. Hyper-Chlorinating. “Super” is simply your normal shock treatment, added after the sun goes down, say to 10 ppm. By morning, the level has dropped to 5 ppm perhaps and by mid-afternoon, levels are down below 2 ppm.

Hyper-Chlorinating, on the other hand, is to raise chlorine levels very high, say to 20 ppm or higher, and hold it there, with continuous additions of sanitizer (shock), to maintain the high chlorine level for up to 24 hours of time, or longer based upon the water conditions. Hyper-chlorination is used for very difficult to eradicate protozoan parasites, such as cryptospridium or to a lesser degree, the giardia parasite.

Hyper-chlorination is not necessary for the removal of your everyday bacteria or viruses, even the Coronavirus. You can disinfect your pool in most cases, with the suggested dosage listed on the bag of pool shock oxidizer.


In The Swim is here for you during this pandemic, and is open to provide support and sanitizers to our customers in need. We’ve also lowered prices on the most commonly purchased pool sanitizers and oxidizers.

If you have any questions about pool sanitizers, oxidizers or disinfectants, and how to keep your pool safe and clean – Leave a Reply below, I answer them personally!

 

Dr. Pool

Dr. Pool

 

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