40 C.F.R. § 141.561
What happens if my system's turbidity monitoring equipment fails?
Cite as 40 C.F.R. § 141.561 (2026)
If there is a failure in the continuous turbidity monitoring equipment, your system must conduct grab sampling every four hours in lieu of continuous monitoring until the turbidimeter is back on-line. Your system has 14 days to resume continuous monitoring before a violation is incurred.