Sanitary Engineering Division

Recommended Pool Disinfecting Procedures

Our best current recommendation for handling fecal accidents is to treat any accident involving unformed stool as a possible Cryptosporidium contamination and disinfect accordingly.

The following steps need to be taken if a pool is either suspected of or is known to be contaminated with Cryptosporidium.

1. Close the pool and notify the local public health authorities, remove as much fecal material as possible.
   
   
2. Add chlorine to raise the disinfectant residual to 20 ppm. Stabilize the pH between 7.2 to 7.5 so the chlorine is effective. (Remember high levels of chlorine can cause a purple interference color when using phenol red to test for pH. If this happens, neutralize the sample with a small amount of sodium thiosulfate.) Run the recirculation equipment for 8 hours with high level of chlorine.
   
   
3. Clean and brush down the walls of the pool, the skimmers housings, and skimmer baskets.
   
   
4. Backwash the filter thoroughly. If this is a whirlpool, drain the pool at this time.
   
   
5. Disinfect the filter.
   
   
   • Sand filters - add a gallon of chlorine bleach (sodium hypochlorite) directly into the filter and let stand for 4 - 6 hours (more may be needed with filters over 36" diameter). Backwash again.
   • Cartridge filters - remove the cartridge and clean the filter casing thoroughly with a 200 ppm solution of chlorine bleach (sodium hypochlorite). Allow to stand for several hours. Clean the cartridge thoroughly and soak in a 200 ppm solution of bleach. Rinse and allow to dry completely.
   • Diatomaceous Earth (D.E.) Filters - Clean the D.E. off the filters, dispose of the D.E., and soak the tank and septums in a 100 ppm solution of bleach.
     
     
6. Restart the recirculation system and adjust the chlorine slowly back to normal, and if the pool is a whirlpool, fill at this time.
   
   
7. Balance the water and reopen.
   
   
8. Monitor the disinfectant levels carefully.
   

Additional assistance can be obtained by calling your local health department. For more specific information on this procedure, please call the Sanitary Engineering Section at (402) 444-7485.