Section Env-Ws 380.17 - Monitoring of Residual Disinfectant Concentration for Systems That Do Not Provide Filtration(a) The residual disinfectant concentration of the water entering the distribution system shall be monitored continuously, and the lowest value shall be recorded each day.(b) If there is a failure in the continuous monitoring equipment, the system owner shall conduct grab sampling every 4 hours in lieu of continuous monitoring, but for no more than 5 working days following the failure of the equipment.(c) A system serving 3,300 or fewer people may take grab samples in lieu of providing continuous monitoring on an ongoing basis at the frequencies prescribed in Table 380-10 below: Table 380-10
Disinfectant Residual Samples For Unfiltered Systems
| System by population | Samples/day |
| <500 | 1 |
| 501 - 1,000 | 2 |
| 1,001 - 2,500 | 3 |
| 2,501 - 3,300 | 4 |
(d)The day's samples taken according to (c) shall not be taken at the same time; and(e) If at any time the residual disinfectant concentration falls below 0.2 mg/l in a system using grab sampling in lieu of continuous monitoring, the system shall take a grab sample every 4 hours until the residual concentration is equal to or greater than 0.2 mg/1.N.H. Code Admin. R. Env-Ws 380.17
#5098, eff 3-18-91, EXPIRED 3-18-97
New. #6521, eff 6-4-97 (See Revision Note at chapter heading for Env-Ws 300); ss by #8352, eff 5-14-05 (formerly part of Env-Ws 380.22 )