---
kind: "range"
citation: "40 C.F.R. §§ 141.550–141.553"
title: "40"
from: "141.550"
to: "141.553"
count: 4
url: "https://uscodex.org/cfr/40/141.550..141.553"
---

# §141.550. Is my system required to meet subpart T combined filter effluent turbidity limits?


All [subpart H](/cfr/40/subpartH.md) systems which serve populations fewer than 10,000, are required to filter, and utilize filtration other than slow sand filtration or diatomaceous earth filtration must meet the combined filter effluent turbidity requirements of [§§ 141.551-141.553](/cfr/40/141.551-141.553.md). If your system uses slow sand or diatomaceous earth filtration you are not required to meet the combined filter effluent turbidity limits of [subpart T](/cfr/40/subpartT.md), but you must continue to meet the combined filter effluent turbidity limits in [§ 141.73](/cfr/40/141.73.md).


# §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)](/cfr/40/141.74.md?p=a) and [(c)](/cfr/40/141.74.md?p=c). Monthly reporting must be completed according to [§ 141.570](/cfr/40/141.570.md). The following table describes the required limits for specific filtration technologies.
- (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)](/cfr/40/141.74.md?p=a) and [(c)](/cfr/40/141.74.md?p=c). Monthly reporting must be completed according to [§ 141.570](/cfr/40/141.570.md). The following table describes the required limits for specific filtration technologies.

# §141.552. My system consists of “alternative filtration” and is required to conduct a demonstration—what is required of my system and how does the State establish my turbidity limits?

- (a) If your system consists of alternative filtration(filtration other than slow sand filtration, diatomaceous earth filtration, conventional filtration, or direct filtration) you are required to conduct a demonstration (see tables in [§ 141.551](/cfr/40/141.551.md)). Your system must demonstrate to the State, using pilot plant studies or other means, that your system's filtration, in combination with disinfection treatment, consistently achieves:
  - (1) 99 percent removal of Cryptosporidium oocysts;
  - (2) 99.9 percent removal and/or inactivation of Giardia lamblia cysts; and
  - (3) 99.99 percent removal and/or inactivation of viruses.
- (b) [Reserved]

# §141.553. My system practices lime softening—is there any special provision regarding my combined filter effluent?


If your system practices lime softening, you may acidify representative combined filter effluent turbidity samples prior to analysis using a protocol approved by the State.