Aquatic facilities prevent recreational water illnesses (RWIs) by layering protections: keeping disinfectant and pH in range, training staff, responding correctly to fecal incidents, designing in extra disinfection where the risk is highest, and getting swimmers to shower, stay out when sick and take bathroom breaks. No single step is enough on its own, because the germ behind most pool outbreaks can survive in properly chlorinated water for days.
The 12 steps below follow the structure of CDC’s prevention steps for pool staff, updated with current CDC guidance.
How common are pool-related outbreaks?
They are reported every year. From 2015 to 2019, CDC received reports of 208 outbreaks linked to treated recreational water (pools, hot tubs and water playgrounds), causing at least 3,646 illnesses, 286 hospitalizations and 13 deaths (Hlavsa et al., MMWR, 2021). Of the outbreaks with a confirmed cause, Cryptosporidium (Crypto) caused 76 outbreaks and 2,492 illnesses, and Legionella caused 65 outbreaks and all 13 deaths. Hotels, motels, lodges, inns and resorts were linked to 71 (34%) of the 208 outbreaks.
Why doesn’t chlorine alone stop every recreational water illness?
Crypto is extremely tolerant to chlorine. CDC reports that at 1 ppm free chlorine, Crypto oocysts can survive for more than 7 days in pool water, so the parasite can spread even in a pool that is properly chlorinated (Hlavsa et al., MMWR, 2021). That is why prevention depends on swimmer hygiene, fast incident response and, at higher-risk venues, an added disinfection system that works alongside chlorine.
Step 1: Make illness prevention a priority before an outbreak
Prevention starts with leadership. Put RWI prevention in writing: who tests the water, who responds to an incident, who talks to the health department and who has authority to close the pool. Budget for training, test equipment and signage, and review the plan each season.
Step 2: Partner with your health department and other facilities
Know your local inspector and your state or local pool code before there is a problem. Health departments can share outbreak alerts and help with incident response, and nearby facilities can share lessons and coordinate if illness spreads between pools. For the violations inspectors find most often, see Why Do Commercial Pools Fail Health Inspections or Get Shut Down?
Step 3: Train pool staff on water quality and RWIs
CDC advises operators to get the operator and chemical handling training their state or local authority recommends (CDC, 2025). Train every staff member who works on deck, not only the operator, to recognize a fecal incident, clear the water and follow the response plan.
Step 4: Teach swimmers and parents how to keep germs out of the water
Swimmers bring most germs into the pool, so education is one of the cheapest protections. CDC asks swimmers to (CDC, 2025):
- Stay out of the pool if they have diarrhea.
- Shower for at least 1 minute before getting in.
- Not swallow the water.
- Take kids on bathroom breaks and check diapers every hour, and change diapers away from the poolside.
For a guide written for swimmers and parents, see How to Avoid Crypto in Swimming Pools.
Step 5: Keep water quality and equipment in range
CDC’s operating guidance for public pools is to keep pH at 7.0 to 7.8 and free chlorine at a minimum of 1 ppm, and to test pH and disinfectant levels at least twice a day, or hourly when the pool is busy (CDC, 2025). For hot tubs, CDC’s minimum is 3 ppm free chlorine. Keep pumps, filters and feeders maintained so circulation and disinfection never lapse. A daily routine helps; see The Commercial Pool Maintenance Checklist.
Step 6: Design the facility for illness prevention
Filtration, circulation and disinfection equipment set the baseline for how well a pool handles germs. The 2024 Model Aquatic Health Code (MAHC), CDC’s model guidance for public pools, describes secondary disinfection as systems installed in addition to the standard required systems, and calls for them at increased-risk aquatic venues such as spray pads, wading pools, venues designed for children under 5 and therapy pools (CDC, 2024 MAHC). The MAHC is a model code, so check which edition your state or local code follows.
Clear Comfort’s hydroxyl-based AOP is a supplemental system that works alongside a low chlorine residual. In a 2014 University of Colorado Boulder lab test, the Clear Comfort system achieved up to 99.99% (4-log) inactivation of Crypto by the 60-minute sample, in dechlorinated lab water held at constant conditions (University of Colorado Boulder, 2014). Results in a working pool depend on flow, turnover and bather load, and the system does not replace the fecal incident response in step 7. For a comparison of options, see Which Pool Sanitation System Is Best for an Aquatic Facility?
Step 7: Set disinfection guidelines for fecal incidents
Write down exactly what staff do when feces are found in the water, and practice it. CDC’s 2018 fecal incident response recommendations (CDC, 2018) include:
- Close the pool (and every pool on the same filtration system) and keep swimmers out until disinfection is done.
- Remove the feces with a net or bucket. Do not vacuum it.
- Formed stool: raise free chlorine to 2 ppm, keep pH at 7.5 or lower, and hold it for 25 to 30 minutes.
- Diarrhea: hyperchlorinate with unstabilized chlorine to a CT value of 15,300, for example 20 ppm for 12.75 hours with no chlorine stabilizer in the water. If stabilizer is present at 1 to 15 ppm, CDC lists 20 ppm for 28 hours. After a diarrheal incident, backwash the filter thoroughly to waste.
- Log the incident: date and time, type of incident, chlorine and pH readings, the steps taken and the disinfection time before reopening.
The 2024 MAHC also added dilution credits for draining and refilling to lower the stabilizer level during a diarrheal incident response (NACCHO, 2024). Follow your state or local code where it differs.
Step 8: Keep restrooms and changing areas clean and close by
Swimmers are more likely to take a bathroom break when restrooms are clean, stocked and near the pool. Provide diaper-changing stations away from the pool deck, with handwashing nearby, so diapers are never changed poolside (CDC, 2025).
Step 9: Schedule hourly bathroom breaks
A regular break clears the pool, gets kids to the restroom and gives staff time to test the water. CDC recommends taking kids on bathroom breaks and checking diapers every hour (CDC, 2025).
Step 10: Set rules for large groups of young children
Camps, day care groups and swim lessons bring many young swimmers in at once. Give group leaders a short orientation on staying out when sick, bathroom breaks and diaper changes before the group swims. Where you can, keep toddlers in a separate wading pool or play area; under the 2024 MAHC, wading pools and venues for children under 5 are increased-risk venues that call for secondary disinfection (CDC, 2024 MAHC).
Step 11: Post and share healthy swimming information
Signs at the entrance, in locker rooms and by the showers remind swimmers of the habits in step 4. CDC offers free posters, fact sheets and graphics on preventing swimming-related illnesses that facilities can download and share (CDC Healthy Swimming communication resources).
Step 12: Plan for outbreaks and emergencies
Have a written plan for an illness report or outbreak: who calls the health department, how records are pulled, when the pool closes and how members are told. Include chemical emergencies too; CDC’s aquatics toolkit covers pool chemical emergencies. Train staff on the plan and review it after every incident.
Frequently asked questions
What causes most recreational water illness outbreaks at pools?
In CDC’s 2015 to 2019 data, Cryptosporidium caused 76 outbreaks and 2,492 illnesses, and Legionella caused 65 outbreaks and 13 deaths. Together they were the leading causes among outbreaks with a confirmed cause.
How long can Crypto survive in a chlorinated pool?
CDC reports that Crypto oocysts can survive for more than 7 days in water with 1 ppm free chlorine. That is why swimmers with diarrhea should stay out of the water and why diarrheal incidents need hyperchlorination.
What should a pool operator do after a diarrheal incident?
Close the pool, remove the material without vacuuming, and hyperchlorinate to a CT value of 15,300, for example 20 ppm free chlorine for 12.75 hours with pH at 7.5 or lower and no stabilizer present. Backwash the filter to waste afterward and log every step, following CDC’s 2018 recommendations and your local code.
Does the Model Aquatic Health Code require secondary disinfection?
The 2024 MAHC calls for secondary disinfection at increased-risk aquatic venues, such as spray pads, wading pools, venues for children under 5 and therapy pools. The MAHC is model guidance, so the rules that apply to a facility depend on its state or local code.
How often should pool operators test chlorine and pH?
CDC advises testing pH and disinfectant levels at least twice a day, and hourly when the pool is in heavy use. CDC’s targets for public pools are pH 7.0 to 7.8 and a minimum of 1 ppm free chlorine.
Can Clear Comfort replace chlorine at a public pool?
No. Clear Comfort’s hydroxyl-based AOP is a supplemental system that works with a low chlorine residual, which is still required. In a 2014 University of Colorado Boulder lab test it achieved up to 99.99% (4-log) Crypto inactivation by the 60-minute sample, under lab conditions.
Planning supplemental disinfection for your facility? See Clear Comfort’s commercial AOP systems.
