{"data":{"id":"us/40-cfr-141.551","jurisdiction":"us","citation":"40 CFR 141.551","heading":"What strengthened combined filter effluent turbidity limits must my system meet?","body":"Your system must meet two strengthened combined filter effluent turbidity limits.\n(a) The first combined filter effluent turbidity limit is a “95th percentile” turbidity limit that your system must meet in at least 95 percent of the turbidity measurements taken each month. Measurements must continue to be taken as described in § 141.74(a) and (c). Monthly reporting must be completed according to § 141.570. The following table describes the required limits for specific filtration technologies.\nIf your system consists of * * * Your 95th percentile turbidity value is * * *\n(1) Conventional Filtration or Direct Filtration 0.3 NTU.\n(2) All other “Alternative” Filtration A value determined by the State (not to exceed 1 NTU) based on the demonstration described in § 141.552.\n(b) The second combined filter effluent turbidity limit is a “maximum” turbidity limit which your system may at no time exceed during the month. Measurements must continue to be taken as described in § 141.74(a) and (c). Monthly reporting must be completed according to § 141.570. The following table describes the required limits for specific filtration technologies.\nIf your system consists of * * * Your maximum turbidity value is * * *\n(1) Conventional Filtration or Direct Filtration 1 NTU.\n(2) All other “Alternative Filtration” A value determined by the State (not to exceed 5 NTU) based on the demonstration as described in § 141.552.","path":["Title 40—Protection of Environment","CHAPTER I—ENVIRONMENTAL PROTECTION AGENCY","SUBCHAPTER D—WATER PROGRAMS","PART 141—NATIONAL PRIMARY DRINKING WATER REGULATIONS","Subpart T—Enhanced Filtration and Disinfection—Systems Serving Fewer Than 10,000 People"],"source_url":"https://www.ecfr.gov/api/versioner/v1/full/2026-08-25/title-40.xml","current_through":"2026-08-25","vintage":"","retrieved_at":"2026-08-27T02:26:04Z","sha256":"75bf5989e6d9d558dfbf6a625a1b0a64d24abb7a706ef2b3262b75b3cff739f4","source_id":"us-cfr","stale":true,"prev":"us/40-cfr-141.550","next":"us/40-cfr-141.552"},"notice":"GroundRules: Original legal text. Not legal advice."}