Every commercial pool will eventually have a fecal incident. The right response protects swimmers, defends the facility legally, and gets the pool back open as fast as safely possible. These are the CDC-aligned protocols.
The three categories (and why they're different)
| Type | Primary risk | Response |
|---|---|---|
| Formed stool | Giardia-class pathogens | 1 ppm FC for 25+ min (CT ≈ 25) |
| Diarrheal stool | Cryptosporidium | 20 ppm FC for 12.75 hrs (CT ≈ 15,300) |
| Vomit / blood (non-diarrheal) | Bloodborne pathogens, Norovirus | Treat as formed stool: 2 ppm FC × 25 min (CDC). Escalate to diarrheal protocol if origin is diarrheal or contains visible diarrhea. |
Formed stool protocol
- Instruct swimmers to leave the pool. Do not let anyone back in.
- Remove the stool with a net or bucket. Discard in a trash bag.
- Disinfect the scoop/net with bleach before reusing.
- Raise free chlorine to 2 ppm if below. Hold pH 7.2–7.5.
- Run circulation for 25 minutes minimum (enough for CT ≥ 50 ppm·min).
- Vacuum to waste any sediment.
- Document: time, operator, chlorine readings, action. Reopen.
Diarrheal stool protocol (the Crypto protocol)
This is the same as the Crypto hyperchlorination response — because you assume it contains Crypto until proven otherwise.
- Close the pool immediately. Post signage.
- Remove as much of the stool as possible.
- Reduce CYA to < 15 ppm if currently higher. Partial drain/refill.
- Adjust pH to 7.5 or below.
- Raise free chlorine to 20 ppm with unstabilized chlorine.
- Hold for 12.75 hours, testing and redosing every 2–4 hours.
- Replace or chemical-soak filter media during the hold.
- Lower FC to normal. Verify. Reopen.
Vomit or blood protocol
Per CDC fecal-incident response, vomit and blood are treated as a formed-stool incident: remove the material, raise free chlorine to 2 ppm, hold pH 7.2–7.5, and run circulation for 25–30 minutes (CT ≥ 25 ppm·min). Diarrheal vomit, or vomit/blood from a swimmer with known illness, escalates to the full diarrheal Crypto protocol (20 ppm FC × 12.75 hr). When in doubt, escalate — but routine vomit does not require a 13-hour pool closure.
Documentation requirements
Every fecal incident must be logged with:
- Date and time of incident
- Incident type (formed / diarrheal / vomit / blood)
- Operator name
- Chlorine and pH readings at start, during hold, and at reopen
- Circulation verification (flow confirmed)
- Action taken, time of reopen, signage posted
Some jurisdictions require reporting diarrheal incidents to the county health department within a specified time window (often 24 hours). Know your local rule.
Preventing next time
- Enforce “no swim with diarrhea” signage and staff vigilance
- Swim-diapers required for children under 3 in kiddie pools
- Scheduled bathroom breaks for children's programs
- Pre-swim showers at all entrances
- Consider UV or ozone secondary disinfection for high-risk venues
Want a pro to handle this?
Our CPO-certified techs run this exact playbook on every weekly service visit.