40 CFR 141.533 - What data must my system collect to calculate a disinfection profile?
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:
(a) The temperature of the disinfected water at each residual disinfectant concentration sampling point during peak hourly flow;
(b) If your system uses chlorine, the pH of the disinfected water at each residual disinfectant concentration sampling point during peak hourly flow;
(c) The disinfectant contact time(s) (“T”) during peak hourly flow; and
(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.