Federal regulations · Through 2026-08-25 · Newer source version available

40 CFR 141.551: What strengthened combined filter effluent turbidity limits must my system meet?

Your system must meet two strengthened combined filter effluent turbidity limits.
(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.
If your system consists of * * * Your 95th percentile turbidity value is * * *
(1) Conventional Filtration or Direct Filtration 0.3 NTU.
(2) All other “Alternative” Filtration A value determined by the State (not to exceed 1 NTU) based on the demonstration described in § 141.552.
(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.
If your system consists of * * * Your maximum turbidity value is * * *
(1) Conventional Filtration or Direct Filtration 1 NTU.
(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.

Where this section sits in the code

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

Your system must meet two strengthened combined filter effluent turbidity limits.

(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.

If your system consists of * * * Your 95th percentile turbidity value is * * *

(1) Conventional Filtration or Direct Filtration 0.3 NTU.

(2) All other “Alternative” Filtration A value determined by the State (not to exceed 1 NTU) based on the demonstration described in § 141.552.

(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.

If your system consists of * * * Your maximum turbidity value is * * *

(1) Conventional Filtration or Direct Filtration 1 NTU.

(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.

Collected 2026-08-27T02:26:04Z. Source file · JSON

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