Don't Smell the Indoor Pool

Guest Blog by David Nance, NSF - #WAHC2017 Sponsor

Indoor Pool air quality smell of cholorineToo often you smell the indoor swimming pool before you see it. And once you see it, you’ll hear about it with the common refrain, “That pool must use a lot of chlorine!” The chlorine-like smell may trick the layperson into thinking this is a normal consequence of the pool being properly managed. However, those in the know will tell you it isn’t the chlorine used to treat the pool you smell but a by-product, chloramines. And smelling an indoor pool isn’t something you should expect and is definitely something you don’t want.

Chloramines form when a chlorine, a strong disinfectant, and oxidant frequently used in pools or spas, reacts with nitrogen compounds in the water. The nitrogen compounds come from many sources, including bather urine and sweat, to form inorganic or organic chloramines. Once formed, the inorganic chloramine may be in one of three varieties: mono-, di- or trichloramine. While monochloramine is a common disinfectant in drinking water treatment, the di- and trichloramines are a one-, two-punch in pools and spas. Chloramine formation ties up free chlorine so it can no longer effectively perform its primary functions of disinfection and oxidation in the pool. 

The di- and trichloramines are known respiratory and ocular irritants. Firsthand experience is enough for most to come to that conclusion. It’s not just bathers and swimmers who need to worry about chloramines for their health. Because the di- and trichloramines are volatile and are present in the air, workers, and anyone in and around the pool can be affected as well. The di- and trichloramines cause the “chlorine” smell common to indoor pools. In addition to direct bather concerns, they can corrode ventilation equipment.

Smelling the waterAs a known health concern and as a hindrance in disinfection and oxidation, many state codes, as well as the CDC’s Model Aquatic Health Code, require the amount of combined chlorine to be monitored and managed. The MAHC sets an action level for the combined chlorine, which contains chloramines, to be at or below 0.4 ppm in the pool. Facility operators can utilize NSF/ANSI 50 certified water quality test devices to accurately determine the combined chlorine content in the water. With an accurate reading of the water chemistry, operators can better manage their facility’s water chemistry to keep below the 0.4 ppm MAHC threshold. To keep below 0.4ppm, preventing and mitigating chloramine formation are key. 

Preventative methods to keep nitrogen compounds out of the pool include improving bather habits such as showering before entering the pool and not urinating in a pool. Both acts are simple and effective at lowering the amount of nitrogen introduced into a pool. While changing bather habits could be the most important way to reduce chloramine formation, facility operators have to manage with existing bather realities in mind. Active management of combined chlorine, and chloramines is the second step.

Several active methods of chloramine mitigation exist. Breakpoint chlorination, or super chlorination, and direct water replacement are two tried and true methods to reduce combined chlorine levels but each has pros and cons. Breakpoint chlorination disrupts schedules as the pool is closed, and water replacement can be a concern with so many cities with water shortages. Ozone and other oxidizers besides chlorine can also mitigate combined chlorine. Another option is to use a water conditioning device designed to reduce combined chlorine. UV and other technologies can fall into this category. A new section of NSF/ANSI 50, the performance and safety standard referenced by the MAHC and most states for equipment and components, is being developed to evaluate products for safety and claims of combined chlorine reduction. 

In addition to managing the water side, ventilation and air flow are equally important to remove any volatile chloramines. Tackling that is a separate discussion with different challenges and solutions. 

Trained professionals, informed bathers and the right equipment are three of the keys to making sure we never smell another indoor pool.

About the Author

Guest Blog by NSF on NSPFDavid Nance 
Business Unit Manager, Water Distribution and Recreational Water Products

David Nance is the Business Unit Manager for NSF International’s municipal water products and recreational water products programs and works with NSF’s global testing, auditing and certification services for distribution system components and recreational water products. Nance has nine years of experience in NSF’s municipal water products program. You can reach out to David at dnance(@) Check out NSF's website, Facebook, Twitter, and Linkedin for more information.


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