Alvaro G. Mendoza

Commercial Energy Specialists, Inc.



Welcome to our “Ask the Expert” feature, designed to assist you with any and all issues related to swimming pool water, mechanical equipment, space conditioning, and code compliance. Ask a question, and we will answer to the best of our ability.


Recently we were asked to provide an explanation and overview of Swim School water quality. What makes it improve, what makes it deteriorate? What are some of the pitfalls? This article will pinpoint these topics, and hopefully will provide a better understanding on which to make swim school treatment decisions.


Swim Schools are tough! No you are not crazy, you are operating one of the toughest pool treatment applications in the industry. Indoor Swim Schools are the toughest, and on par with leading water parks, resort hotels, etc. We mention this so we all know to take water quality very seriously, be attentive on a daily basis, and be ready to apply significant resources to handle the task at hand. Failing to do so usually leads to poor results.


Water, the universal solvent: You can’t see them, but fill water, bathers, chemicals, etc. all add undesirable byproducts and organisms to the pool water. They are invisible, but they are there. Water dissolves these byproducts, organics, and organisms but doesn’t get rid of them, and they can accumulate to cause skin and lung irritation (organics), cause staining (metals), promotes eye burn (chloramines),create a chlorine demand (body wastes), and/or just clutter up the water (TDS).


Water Quality is cumulative! This means that Water Quality improves and deteriorates depending on a handful of variables. You gain momentum and lose momentum. When you shock the pool to resolve a problem, the water can immediately start to deteriorate again moments later if you did not resolve the root of the problem. If you lose enough momentum you can develop a “chlorine demand” that cannot be tested via traditional test methods. Water can then get “sick” and will continually want to degrade. Operators need to better identify the warning signs.


How to gain momentum: You gain momentum by maintaining high ORP levels (>775 mV) on a consistent basis for extended periods of time. Your water will become more “bulletproof” and will recover quicker. You can also blast chloramines


with medium pressure or Amalgam UV on a continuous basis to help chlorine concentrate on the other tasks at hand. You should replace judicious amounts of water in your pool (about an average of 4 gallons per bather) and you should make sure to limit the amount of down time from the high-ORP state.


How to lose momentum: Every time you overload your pool, run out of chlorine, let your pH go high, or wait too long to clean your filters, you are sliding down the “slope”. Watch out for the warning signs, that is LOW ORP levels (<700 mV with chlorine > 3.0 PPM). The lower the ORP, the more trouble you are getting into. Just fixing the problem (filling the chlorine or acid vat, cleaning the filter, etc. corrects the alarm but does not resolve the problem – that is the accumulation of “bad stuff” in the water.


Chlorine alone is mediocre strategy: If you operate a heavily used swim school pool, and are relying on chlorine and pH feed only, you may not have enough weapons in your arsenal. Chlorine is an important yet mediocre oxidizer, has plenty of undesirable byproducts, and will not fulfill the other roles that you need address in your pool. Many leading schools rely on (properly designed and installed) Medium Pressure or Amalgam UV, corona discharge Ozone, Saline Chlorination, etc. to help with the oxidation and disinfection. Also relatively inexpensive professional strength additives can reduce negative effects of organics, metals, and phosphates.


Not going well? Seek advice and assistance: If you are feeling overwhelmed, don’t worry. There are plenty of people around to support you, including a bunch of willing USSSA members who have figured it out. The solutions are normally pretty well documented and affordable, and can be accomplished in baby steps as your swim school cash flow improves.


Please feel free to forward your questions, issues, and comments through the USSSA office, or directly to me via email at


Best Regards, Alvaro G. Mendoza