Execute CDC-specified hyperchlorination remediation to inactivate Cryptosporidium after a confirmed or suspected exposure

Steps

1. Confirm/estimate cyanuric acid concentration first, since CYA above roughly 50 ppm can make CDC's target inactivation level unachievable even at very high chlorine and long contact times
2. If CYA is elevated, dilute the pool toward CDC's recommended 15 ppm or less before starting the hyperchlorination clock
3. Raise and hold free chlorine at the level specified in CDC's current hyperchlorination-to-kill-Cryptosporidium guidance for the pool's CYA level and pH — for CYA-free water at pH 7.5/25°C, CDC's reference point is 20 mg/L free chlorine sustained for about 12.75 hours to reach a CT value of 15,300 mg·min/L (3-log inactivation)
4. Maintain pH in the range specified alongside the FC target, since pH shifts the proportion of active hypochlorous acid
5. Keep the pool closed to bathers for the full duration, run filtration continuously, and backwash/clean or replace filter media afterward per protocol
6. Verify free chlorine has remained at or above target throughout the hold period before reopening; document readings across the full duration