Quick answer
For a formed stool or vomit in a chlorinated pool, CDC guidance is to close the pool, remove the material, raise free chlorine to 2 ppm at pH 7.5 or below and hold it for 25 minutes. For diarrhea, raise free chlorine to 20 ppm at pH 7.5 or below and hold it for 12.75 hours (a CT of 15,300). Log every step.
- Formed stool or vomit: 2 ppm FC, pH ≤ 7.5, 25 minutes.
- Diarrheal stool: 20 ppm FC, pH ≤ 7.5, 12.75 hours (CT 15,300).
- Cyanuric acid slows disinfection — follow CDC/health dept. guidance.
- Blood: closure generally not required in properly chlorinated water.
CDC response steps by incident type
| Incident | Close? | Free chlorine & pH | Hold time |
|---|---|---|---|
| Formed stool | Yes | 2 ppm, pH ≤ 7.5, ~77°F | 25 minutes |
| Vomit | Yes | 2 ppm, pH ≤ 7.5 | 25 minutes |
| Diarrheal stool | Yes | 20 ppm, pH ≤ 7.5, ~77°F | 12.75 hours (CT 15,300) |
| Blood | Generally no | Maintain normal levels | — |
Work out the chlorine dose, hold time and earliest reopening time for your pool with the fecal incident hyperchlorination calculator.
What to write in the incident log
- Date and time of the incident and type (formed, diarrheal, vomit, blood, injury).
- Time the pool was closed and bathers cleared.
- How the material was removed; equipment disinfected.
- Free chlorine and pH at the start of treatment and during the hold.
- Contact time achieved (and CT value for diarrheal incidents).
- Filter backwash after treatment (diarrheal).
- Time reopened, chlorine and pH at reopening, and who approved it.
Why the log matters
Cryptosporidium is chlorine-tolerant and is the leading cause of pool-associated outbreaks in the United States. If illness is reported after an incident, health investigators will ask for your records. A complete incident log showing the CDC procedure was followed is your best evidence.
How to respond to a formed fecal incident in a chlorinated pool
- Close the pool. Clear all bathers from the water and close the pool.
- Remove the material. Remove the stool with a net or scoop and disinfect the tool.
- Raise chlorine. Raise free chlorine to 2 ppm and keep pH at 7.5 or lower.
- Hold. Maintain 2 ppm free chlorine for at least 25 minutes (longer if CYA is present).
- Log and reopen. Record times and readings in the incident log, then reopen when levels are in the normal range.
Frequently asked questions
What do you do if someone poops in a public pool?
Close the pool, remove the stool, and disinfect. For formed stool, raise free chlorine to 2 ppm (pH ≤ 7.5) for 25 minutes. For diarrhea, raise it to 20 ppm for 12.75 hours. Then record everything in the incident log.
For a diarrheal incident, how long do you hold free chlorine at 20 ppm?
12.75 hours (765 minutes) at pH 7.5 or lower and about 77°F, which reaches the CDC target CT value of 15,300. Then backwash the filter and return chlorine to the normal operating range before reopening.
How long do you close a pool after a diarrheal accident?
Under CDC guidance, until free chlorine has been held at 20 ppm (pH ≤ 7.5) for 12.75 hours — a CT of 15,300 — and levels are returned to normal operating range.
Do you close a pool for blood?
CDC guidance says there is generally no public health reason to close a properly chlorinated pool for blood, but deck spills should be cleaned with a bleach solution.
What does CT value mean?
CT is concentration (ppm) multiplied by time (minutes). A diarrheal incident requires a CT of 15,300 — for example, 20 ppm held for 765 minutes (12.75 hours).
This page is an educational summary, not legal advice. Pool and spa codes differ by state and county and change over time — always confirm requirements with the health department that inspects your facility.