---
kind: "section"
citation: "40 C.F.R. § 141.621"
title: "40"
number: "141.621"
heading: "Routine monitoring."
url: "https://uscodex.org/cfr/40/141.621"
---

# §141.621. Routine monitoring.

- (a) **Monitoring.**
  - (1) If you submitted an IDSE report, you must begin monitoring at the locations and months you have recommended in your IDSE report submitted under [§ 141.605](/cfr/40/141.605.md) following the schedule in [§ 141.620(c)](/cfr/40/141.620.md?p=c), unless the State requires other locations or additional locations after its review. If you submitted a 40/30 certification under [§ 141.603](/cfr/40/141.603.md) or you qualified for a very small system waiver under [§ 141.604](/cfr/40/141.604.md) or you are a nontransient noncommunity water system serving <10,000, you must monitor at the location(s) and dates identified in your monitoring plan in [§ 141.132(f)](/cfr/40/141.132.md?p=f), updated as required by [§ 141.622](/cfr/40/141.622.md).
  - (2) You must monitor at no fewer than the number of locations identified in this [paragraph (a)(2)](#a-2).
  - (3) If you are an undisinfected system that begins using a disinfectant other than UV light after the dates in [subpart U](/cfr/40/subpartU.md) of this part for complying with the Initial Distribution System Evaluation requirements, you must consult with the State to identify compliance monitoring locations for this subpart. You must then develop a monitoring plan under [§ 141.622](/cfr/40/141.622.md) that includes those monitoring locations.
- (b) **Analytical methods.** You must use an approved method listed in [§ 141.131](/cfr/40/141.131.md) for TTHM and HAA5 analyses in this subpart. Analyses must be conducted by laboratories that have received certification by EPA or the State as specified in [§ 141.131](/cfr/40/141.131.md).

## Notes

### Amendments

[71 FR 488, Jan. 4, 2006, as amended at 74 FR 30958, June 29, 2009]

### Source

Source: 71 FR 488, Jan. 4, 2006, unless otherwise noted.

### Authority

Authority: 42 U.S.C. 300f, 300g-1, 300g-2, 300g-3, 300g-4, 300g-5, 300g-6, 300j-4, 300j-9, and 300j-11.

### Source

Source: 40 FR 59570, Dec. 24, 1975, unless otherwise noted.

### Amendments

[71 FR 488, Jan. 4, 2006, as amended at 74 FR 30958, June 29, 2009]