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Pool Fouling Guidelines

Fecal incidents are a concern and an inconvenience to both pool and spa operators as well as bathers. Operators should carefully explain to bathers why the recreational water venue needs to be closed in response to a fecal incident. They need to allow for proper disinfection to protect the bather's health. Closures allow chlorine to do its job which is to kill germs and help prevent recreational water illnesses.

Spas, wading pools and some (recirculating) splash or spray pads can have smaller amounts of water. In response to fecal incidents in small volume venues, it might be more efficient to completely drain as much water as possible, scrub and clean all accessible surfaces in contact with the contaminated water, replace or clean filter media when appropriate and refill uncontaminated water from an approved source like a municipal water system.

Pool Fouling Procedures

Niagara Region Public Health advocates following U.S. Centers for Disease Control and Prevention Guidelines regarding fecal contamination. The guidelines concentrate on the deactivation of the germ Cryptosporidium. Cryptosporidium is a treatment resistant, waterborne pathogen or germ. A formed stool presents less of a risk for disease transmission as it acts as a container for the pathogen. As a result, the procedures distinguish three separate approches for water disinfection - formed stool and diarrhea with and without stabilizer in the water.

Formed stool

Step 1: Close the aquatic venue to swimmers. If you have multiple venues that use the same filtration system, all venues will have to be closed. Do not allow anyone to enter the venue(s) until the disinfection process is completed.
Step 2: Remove as much of the fecal matter as possible (using a net or bucket) and dispose of the fecal matter in a sanitary matter. Clean and disinfect the item used to remove the fecal matter (after cleaning, leave the net or bucket immersed in water during disinfection). Vacuuming fecal matter from the water is not recommended.
Step 3: If necessary, clean and disinfect any contaminated pool and deck surfaces using an adequate disinfecting solution (1 part bleach to 9 parts water).
Step 4: Raise the water's free available chlorine (FAC) to at least 2 parts per million (ppm) and ensure that pH is maintained between 7.2 to 7.5. Close pool for additional twenty-five minutes. Other concentrations or closure times may be used (refer to table).
Step 5: Confirm the filtration system is operating while the water reaches and is maintained at the proper free chlorine concentration and pH for disinfection.
Step 6: Allow swimmers back into the water only after the disinfection process has been completed and all water chemistry is within acceptable range as per Ontario Public Pools regulation.
Step 7: Document the incident and details on the daily pool records.

Requirements for formed stool fecal incidents

Free available concentration (ppm) Disinfection time (minutes)
1.0 45
2.0 25
3.0 19

Diarrhea without stabilizer in the water (indoor pools)

Step 1: Close the aquatic venue to swimmers. If you have multiple venues that use the same filtration system, all venues will have to be closed. Do not allow anyone to enter the venue(s) until the hyperchlorination process is completed.
Step 2: Remove as much of the fecal matter as possible (using a net or bucket) and dispose of the fecal matter in a sanitary matter. Clean and disinfect the item used to remove the fecal matter (after cleaning, leave the net or bucket immersed in water during hyperchlorination). Vacuuming fecal matter from the water is not recommended.
Step 3: If necessary, clean and disinfect any contaminated pool and deck surfaces using an adequate disinfecting solution (1 part bleach to 9 parts water).
Step 4: Using unstabilized chlorine (sodium hypochlorite), raise the water's free chlorine concentration (see table below) and maintain water at pH 7.5 or less.
Step 5:

Achieve a concentration x time (CT) inactivation value of 15,300 to inactivate or kill Crypto. The CT inactivation value refers to the concentration of free chlorine in parts per million (ppm) multiplied by the time in minutes at a specific pH and temperature.

Step 6: Confirm the filtration system is operating while the water reaches and is maintained at the proper free chlorine concentration and pH for hyperchlorination.
Step 7: Backwash the filter thoroughly after reaching the CT inactivation value. Be sure to discharge directly to waste and according to state or local regulations. Do not return the backwash through the filter. Where appropriate, replace the filter media.
Step 8: Allow swimmers back into the water only after the required CT inactivation value has been achieved and the free chlorine concentration and pH are within the operating range.
Step 9: Document the incident and details on the daily pool records.

Requirements for diarrhea without stabilizer (indoor pools / spas)

Free available concentration (ppm) Disinfection time (hours)
20 12.75
10 25.5

Diarrhea in water with stabilizer (outdoor pools)

Step 1: Close the aquatic venue to swimmers. If you have multiple venues that use the same filtration system, all venues will have to be closed. Do not allow anyone to enter the venue(s) until the hyperchlorination process is completed.
Step 2: Remove as much of the fecal matter as possible (using a net or bucket) and dispose of the fecal matter in a sanitary matter. Clean and disinfect the item used to remove the fecal matter (after cleaning, leave the net or bucket immersed in water during hyperchlorination). Vacuuming fecal matter from the water is not recommended.
Step 3: If necessary, clean and disinfect any contaminated pool and deck surfaces using an adequate disinfecting solution (1 part bleach to 9 parts water).
Step 4: Using unstabilized chlorine (sodium hypochlorite), raise the water's free chlorine concentration and maintain water at pH 7.5 or less.
Step 5:

Hyperchlorinate. Chlorine stabilizer slows the rate at which free chlorine inactivates or kills Crypto, and the more stabilizer there is in the water the longer it takes to kil Crypto. If the cyanuric acid concentration is 1-15 parts per million (ppm):

  • Raise the free chlorine concentration to 20 ppm for 28 hours or,
  • Raise the free chlorine concentration to 30 ppm for 18 hours or,
  • Raise the free chlorine concentration to 40 ppm for 8.5 hours

If the cyanuric acid concentration is more than 15 ppm, lower the concentration to 1-15 ppm by draining partially and adding fresh water without chlorine stabilizer before attempting to hyperchlorinate.

Step 6: Confirm the filtration system is operating while the water reaches and is maintained at the proper free chlorine concentration and pH for hyperchlorination.
Step 7: Backwash the filter thoroughly after reaching the CT inactivation value. Be sure to discharge directly to waste and according to state or local regulations. Do not return the backwash through the filter. Where appropriate, replace the filter media.
Step 8: Allow swimmers back into the water only after the required CT inactivation value has been achieved and the free chlorine concentration and pH are within the operating range.
Step 9: Document the incident and details on the daily pool records.
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