Fecal and Illness Incident Response

Purpose

This procedure guarantees that a contamination event is classified before anyone reacts, that the water is empty within a minute of discovery rather than at the end of a conversation, and that reopening is gated on a chlorine concentration held for a stated time rather than on the clock, the weather, or how many residents are standing at the fence. The failure this prevents is specific and common: a shop treats a loose stool like a formed one, shocks the pool, reopens in two hours, and a Cryptosporidium outbreak walks through the property over the following two weeks with the shop's own service ticket as the timeline.

Scope

Covers formed stool, diarrheal stool, vomit and blood in residential and semi-commercial pools and spas: HOA and apartment pools, small hotel and gym pools, and private pools where the shop is asked to respond. Covers classification, removal, the disinfection hold, filter handling, the reopening check and the record.

It does not cover routine shock dosing or algae recovery, which the shock dosing and green pool SOPs own, nor acid handling, which the muriatic acid SOP owns. Where the pool is public, the health department's rule governs over this procedure, including its own closure and notification requirements, so call them before you decide the pool is ready.

Roles and responsibilities

Why the hold is a CT value, not a shock

Disinfection is concentration multiplied by contact time, written CT and reported in mg-min per liter. Most of what lands in a pool dies at ordinary chlorine levels in minutes. Cryptosporidium does not: its oocyst wall makes it chlorine tolerant, which is why the two targets below differ by a factor of 306.

Those targets are CDC's fecal incident response recommendations for aquatic staff, which are revised, so pull the current version rather than a laminated card of unknown age. Three conditions gate them and all three are load-bearing. The pH ceiling of 7.5 matters because the fraction of free chlorine present as hypochlorous acid, the form that does the work, falls steeply above it. The stabilizer gate matters because above 15 ppm cyanuric acid CDC does not treat hyperchlorination as reliable, so the water is partly drained and refilled to bring stabilizer to 15 ppm or below before any hold is started. And the temperature and turnover assumptions behind those figures are a well-circulated pool, not a pool with a dead pump.

Procedure

1. Clear the water before anything else, and keep it clear. Every person out, deck cleared back from the edge, gate secured and a closure sign posted. Accept when the water is empty and the sign is up within about two minutes of discovery. Wrong is finishing the conversation with the resident first, which is how somebody's toddler gets back in behind you: order everyone out, then talk. Hazard is contact and ingestion, so put on nitrile gloves before you touch anything, do not handle an ill person yourself, and keep your hands away from your face until you have washed them.

2. Classify the event in writing before you dose anything. Formed stool, diarrheal stool, vomit with stomach contents, or blood, with the time of discovery. Accept when the classification and the time are on the ticket. Wrong is calling a loose stool formed because the property has a party booked, which is the single decision that turns an incident into an outbreak: when it is ambiguous, treat it as diarrheal. Hazard is the same contact and ingestion route, so classify by looking, never by probing with an ungloved hand.

3. Remove the material with a net or scoop, never the vacuum. Lift it out in one pass, double-bag it, put it in the trash. Accept when nothing visible remains and the scoop is either discarded or soaked in a bleach solution per the label. Wrong is vacuuming, which pushes the material through the pump and into the filter and turns a surface problem into a media problem. Hazard is splash and hand-to-mouth transfer, so wear gloves and eye protection, do not spray the spot with a hose to break it up, and wash to the elbows afterward.

4. Test pH and cyanuric acid and correct pH to 7.5 or lower before raising chlorine. Accept when a fresh reagent test reads pH at or below 7.5 and the stabilizer value is written down. Wrong is hyperchlorinating at pH 7.9, where much of the free chlorine sits in the weaker form and the hold you are about to time does not deliver the CT you think it does. Stop if stabilizer exceeds 15 ppm: partial drain and refill to bring it to 15 or below, then start over. Hazard is acid, so follow the acid SOP, keep it away from the hypochlorite you are about to use, and never let the two share a vessel or a feeder.

5. Raise free chlorine to the classified target and start the clock only when the target is confirmed at two sample points. Accept when both readings meet or exceed target and the confirmation time is logged to the minute. Wrong is starting the clock when you finished pouring, which credits you a half hour of mixing you did not get. Hazard is the oxidizer, so keep hypochlorite off skin and eyes, add calcium hypochlorite to water rather than water to it because it heats, and dose from upwind of the pour.

6. Run circulation and filtration for the whole hold and re-test free chlorine at intervals no longer than four hours. Accept when every reading is at or above target and each is logged with its time. Wrong is a reading that has drifted below target with the clock still running, which invalidates the hold that has already elapsed. Stop rule: on any reading below target, re-dose, re-confirm and restart the clock from the new confirmation time. Hazard is the pump: nobody swims, nobody reaches into a skimmer, and the pool stays signed and secured for the full hold rather than only overnight.

7. After the hold, handle the filter as contaminated. Backwash sand or DE to waste, never back to the pool, and replace cartridge or DE media after a diarrheal event. Accept when spent media is bagged and gone and the tank is reassembled with the manufacturer's air relief open until water flows. Wrong is returning backwash water to the pool, which re-seeds it. Hazard has two routes here: gloves for the contact route, and spent DE is a respirable dust, so wet it down, never sweep or blow it dry, and use respiratory protection only under a written program per 29 CFR 1910.134.

8. Bring chlorine back into the operating range, then verify the water before the sign comes down. Accept only when free chlorine is inside the pool's own logged operating band, pH sits between 7.2 and 7.8, and the main drain is clearly visible from the deck. Wrong is reopening at hold concentration because the hours have elapsed, which sends swimmers into water that will burn eyes and bleach suits. Stop and hold the closure if any one of the three fails. Hazard is that this is the step putting people back in the water, so remove the sign only after all three checks are written down, and open the gate yourself rather than telling someone else it is fine.

9. Write the incident record and hand it over, then notify where notification is required. Accept when the operator holds a copy showing the classification, the hold, every chlorine reading and the reopening time. Wrong is a verbal handover, which leaves the shop with nothing when someone asks what was done. On a public pool, call the health department the same day and record who you spoke to. Hazard: none at this step, it is paperwork at the tailgate, and it is the only part of the response that survives the season.

The record this produces

One incident record per event, filed on the pool's job record and readable by someone reconstructing the week months later.

• Discovery: time, who found it, classification and the reason for it.
• Removal: method, time, what was done with the scoop.
• Water before dosing: pH, free chlorine, cyanuric acid, temperature.
• The hold: target, confirmation time at two points, every interval reading with its time, and any restart with the reason.
• Filter: action taken, where backwash water went, media replaced or not.
• Reopening: free chlorine, pH, clarity check, time the sign came down, who removed it.
• Notification: agency, person spoken to, time.

Worked pass: 24-unit apartment pool, diarrheal incident

Discovery 14:05 Tuesday. Pool cleared and signed at 14:07. Classified diarrheal on sight. Material netted and bagged at 14:12.

Step 4. pH read 7.8, cyanuric acid 12 ppm. Stabilizer is inside the 1 to 15 ppm band, so the 28 hour row governs rather than the 12.75 hour row, and no drain is required. Acid added per the acid SOP; pH re-tested at 14:55 and read 7.4, inside the 7.5 ceiling.

Step 5. Free chlorine raised and confirmed at 20 ppm and 21 ppm at the two sample points at 15:20. Clock started 15:20 Tuesday, which puts the earliest end at 19:20 Wednesday.

Step 6 FAILS. Readings held at 20 ppm through the 19:00 and 23:00 checks. The 09:00 Wednesday check read 16 ppm, below the 20 ppm target, so the hold as written was not satisfied and the elapsed 17 hours 40 minutes does not count. Stop rule taken: re-dosed, re-confirmed 20 ppm at both points at 09:40 Wednesday, clock restarted. New end time 09:40 Wednesday plus 28 hours, which is 13:40 Thursday. The property was told the new time in writing the same morning, because a reopening promised for Wednesday evening and quietly slipped to Thursday afternoon is how a resident ends up climbing the fence.

Step 7. Cartridge element replaced Thursday afternoon rather than cleaned, the old element bagged and binned. Nothing was backwashed to the pool.

Step 8. Free chlorine still read 11 ppm at 14:00 Thursday, outside the pool's logged 2 to 4 ppm band, so the closure held rather than reopening on the elapsed hold alone. Friday 08:00: free chlorine 3.6 ppm, pH 7.5, main drain clearly visible. All three checks pass, so the sign came down at 08:15 Friday with the technician opening the gate.

Step 9. Record handed to the property manager, health department called Tuesday afternoon at classification rather than after the reopen, contact name logged.

Two things in that run are worth carrying. The failed reading at 09:00 cost roughly 18 hours, and it cost them because the clock restarts rather than resumes, which is the whole reason the interval checks exist. And the pool was not ready when the hold ended: the hold and the reopening check are two separate gates, and the second one failed first.

References

• CDC fecal incident response recommendations for aquatic staff and the Model Aquatic Health Code, in their current revision, which are the source of the CT targets above.
• Your state or county public pool code, which sets the closure and notification duties on a public pool and governs where it differs.
• 29 CFR 1910.134 for respiratory protection, which is a written-program requirement rather than a box of dust masks, referenced here for spent filter media.
• See related: Shock Dosing Standard; Filter Cleaning and Media Replacement; Muriatic Acid Handling and Dilution.