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The wonderful capabilities of chlorine

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The mystery of breakpoint chlorination

In many cases, pool operators will erroneously attempt to breakpoint organic chloramines. Because of the presence of urea, this will lead to dangerous tri-chloramines being formed. This occurrence is especially detrimental at indoor facilities as tri-chloramines are volatile and will spread as a noxious gas throughout the building.

Breakpoint chlorination is a practice that came from the wastewater and drinking water industry and was primarily used for breaking apart ammonia from chlorine. How the practice made its way into the pool industry is somewhat a mystery.

For pools, the typical practice of breakpoint is to test and determine the amount of combined chlorine or chloramines present and then add 10 times the parts per million in free chlorine. The theory is that it would take 10 molecules of free chlorine to break apart one molecule of combined chlorine.

Current research has shown this amount is overkill—even in the practice for drinking water—as  less free chlorine is required to separate ammonia from chlorine. Many studies indicate no more than 4 ppm of chlorine will accomplish the breakpoint of ammoniated chlorine. It is important to keep in mind this technology came from industrial water treatment and not the pool industry. Additionally, as pointed out earlier, with the presence of excessive organic load from swimmers, breakpoint techniques will only lead to the creation of dangerous tri-chloramines. Therefore, the question remains “what is the proper solution to this challenge of water treatment?” The following are some alternatives that can help ensure clean and sanitized water that is relatively free from dangerous chlorine disinfection byproducts.

  • Practice pro-active oxidation with non-chlorine shock monopersulfate (MPS).
  • Incorporate the use of ozone, UV, or both.
  • Enhance the filter’s ability to remove organic contaminants with the use of clarifier flocculants.
  • In heavy-use pools with high oils use an enzyme to digest and breakdown organic waste.
  • Keep filters clean.
  • Practice maintenance dilution of the water (in Europe, many pools have a system of doing daily dilutions in equal amounts so the entire contents of the pool is being diluted and replaced within 30 days).
  • For public facilities, an enforced rule for mandatory bather showers and bathroom breaks for smaller children and swim teams should be developed.
  • Rather than resorting to typical breakpoint, try gradually increasing the free chlorine over time until demand ceases. Then slowly add free chlorine to reach residual.

Chlorine is an amazing element with wonderful capabilities to keep pools clear, clean, and safe. However, like any chemical, it must be used correctly to accomplish its intended purpose.


Pool Operators Manual, published by Washington State Public Health Association (1997).

The Chlorine Revolution-Water Disinfection and the Fight to Save Lives by Michael J. McGuire (2013)

Pool and Spa Operators Handbook, published by the National Swimming Pool Foundation (NSPF) (2017)

Service Tech Manual 4th Edition, published by the Association of Pool and Spa Professionals (APSP) (2013)

Water Pure and Simple: The Infinite Wisdom of an Extraordinary Molecule, by Paolo Consigli, MD (2008)

The World of Carbon, by Isaac Asimov (1962)

Pool Chlorination Facts, by Robert W. Lowry (2003)

The Elements: An Illustrated History of Chemistry, by Tom Jackson (2018)

Terry Arko has more than 40 years of experience in the pool, spa and hot tub industry, working in service, repair, retail sales, chemical manufacturing, and product development. He is a certified pool operator (CPO) instructor through the National Swimming Pool Foundation (NSPF). He also serves as instructor for the Pool Chemistry Training Institute (PCTI) to certify residential pool techs. Arko is an active member on the Association of Pool and Spa Professionals (APSP) Recreational Water Quality Committee (RWQC). He is a member of Pool & Spa Marketing’s Editorial Advisory Committee and currently serves as a water specialist for NC Brands, maker of SeaKlear, Natural Chemistry, and Coral Seas. He can be reached via e-mail at

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