StacksVerified U.S. regulatory reference

40 CFR §141.533

Verified against eCFR.gov as of June 20, 2026View official text on eCFR.gov ↗
Your system must monitor the following parameters to determine the total log inactivation using the analytical methods in § 141.74 (a), once per week on the same calendar day, over 12 consecutive months:
  1. (a)The temperature of the disinfected water at each residual disinfectant concentration sampling point during peak hourly flow;
  2. (b)If your system uses chlorine, the pH of the disinfected water at each residual disinfectant concentration sampling point during peak hourly flow;
  3. (c)The disinfectant contact time(s) (“T”) during peak hourly flow; and
  4. (d)The residual disinfectant concentration(s) (“C”) of the water before or at the first customer and prior to each additional point of disinfection during peak hourly flow.