A total coliform-positive sample does not disappear because the operator thinks the tap was wrong. 40 CFR 141.853(c) is the invalidation rule under the Revised Total Coliform Rule. The state may invalidate a total coliform-positive result, and only on the grounds that section names. A laboratory may also invalidate a sample for interference. You, as the operator, do not void the result by rewriting the chain of custody or by taking a private follow-up bottle to a different bench.
This page is who may invalidate, what evidence the rule accepts, and why an invalidated bottle does not finish the month. It is not the monthly sample-count table: Total coliform sampling frequency under the RTCR. It is not the siting plan: Coliform sample siting plan requirements. Confirm an invalidation request with your primacy agency. Wyoming, the District of Columbia, and tribal systems ask the EPA region with primacy. This isn't legal advice.
Who may invalidate, and who may not
141.853(c)(1) says the State may invalidate a total coliform-positive sample only if one of three conditions is met. The system does not hold that pen. A board vote does not.
A certified laboratory has a narrower job. 141.853(c)(2) requires the lab to invalidate a total coliform sample, unless total coliforms are actually detected, when the culture is unreadable (interference). If the lab already detected total coliforms, that clause does not let anyone throw the positive away. You do not mark the result "void" on your own log and skip the repeats. An unofficial void is how a single TC+ becomes a missed-repeat Level 1.
The three grounds in 141.853(c)(1)
The state may invalidate a total coliform-positive sample only if:
- Improper sample analysis. The laboratory establishes that improper analysis caused the total coliform-positive result. That is a lab error the lab owns in writing: wrong method, contaminated media, a mix-up of bottles, a quality-control failure. A verbal "we think it was the bench" is not enough. Ask the lab for the written statement the state will accept, and send it to the primacy contact with the PWSID and the sample number.
- A domestic or other non-distribution plumbing problem, proved by the repeats. 141.853(c)(1)(ii) is strict. The state may use the repeat-sample results only if every repeat collected at the same tap as the original total coliform-positive is also total coliform-positive, and every repeat collected somewhere other than that original tap is total coliform-negative. The state cannot invalidate on repeats if all the repeats are negative. The state also cannot use this ground if the system has only one service connection. This is the "the hose bib was the problem, the distribution was not" path. It is not available just because you dislike the original tap.
- Substantial grounds that the result does not reflect distribution water quality. 141.853(c)(1)(iii) is the state's judgment call. The decision and the supporting rationale must be documented in writing, and approved and signed by the supervisor of the State official who recommended the decision. A phone call is not that document. Typical facts operators bring: the sample was taken at a tap the siting plan does not name, the bottle was unpreserved or past hold time, the sampler was not the person on the plan, or a documented cross-connection sat on that line that day. Typical facts that do not carry the decision by themselves: "we never had a positive before," "the well looks fine," or "the board is sure the water is good."
On that third ground the rule is explicit about repeats. The system must still collect every repeat required under 40 CFR 141.858(a), and must use those repeats to decide whether a coliform treatment-technique trigger in 141.859 has been exceeded. The state may not invalidate a total coliform-positive sample solely because all the repeats came back negative. Clean repeats are good news. They are not, by themselves, an invalidation.
An invalidated sample does not count, so you still owe a valid one
141.853(c) opens with the consequence: a total coliform-positive sample invalidated under that paragraph does not count toward meeting the minimum monitoring requirements. Invalidation is not a free month. You still need a valid sample for the period.
If the laboratory invalidated the bottle for interference under 141.853(c)(2), the system must collect another sample from the same location as the original sample within 24 hours of being notified of the interference, and have it analyzed for total coliforms. You keep resampling within 24 hours until you have a valid sample. The state may waive the 24-hour limit on a case-by-case basis. Ask for that waiver in writing if weather, access, or a closed building makes the same-day resample impossible.
If the state invalidated a total coliform-positive under 141.853(c)(1), ask the primacy contact, the same day, which replacement sample they want and whether the original repeats still stand. Do not invent a replacement site. Use the siting plan: Coliform sample siting plan requirements. Routine monthly counts still live on the frequency page.
Call a state-certified drinking-water lab. Method, bottle, and hold time have to match: How to choose a state-certified drinking water lab.
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What you still owe while the state decides
Invalidation is a state decision. The clocks that started when the lab called do not pause while you wait for that decision.
- Repeats. 40 CFR 141.858 still requires a set of repeat samples, usually within 24 hours of the TC+ notice, unless the state extends that window in writing. Missing those repeats is itself a Level 1 trigger. See How to prepare for an RTCR Level 1 assessment. How to place and time those bottles is a different write than this one.
- E. coli. A total coliform-positive bottle is tested for E. coli. An E. coli-positive result is an acute path, not an invalidation debate. See E. coli and total coliform violation response and, if a Level 2 is triggered, How to prepare for an RTCR Level 2 assessment.
- Triggered source monitoring. A groundwater system with a routine TC+ still has the Groundwater Rule source-sample clock. Invalidation of the distribution bottle, if it comes, does not automatically cancel a source sample the state already told you to take. See Groundwater Rule triggered source water monitoring.
Collect the repeats. Collect the replacement if the lab rejected the bottle. Write the invalidation request as a separate letter. Put the PWSID, the sample number, the collection date, the site ID from the siting plan, the lab's written error statement if you have one, and the ground in 141.853(c)(1) you are asking the state to use. Ask for a written decision. Keep the request, the decision, the repeats, and the replacement with the coliform file. 40 CFR 141.33 keeps coliform records for five years. See water system record retention.
The hour the lab calls: write the notification time, start the repeat set, and do not wait for invalidation. If the culture was unreadable, resample the same location within 24 hours. If you believe the analysis or the tap was wrong, send that in writing with the PWSID and the sample number. Do not skip next month's routine because this bottle is under review.
FAQ
Can I invalidate a total coliform-positive myself if I know the tap was a hose bib?
No. The state may invalidate. You may send evidence. You still collect the repeats and any replacement sample the state or the lab requires. Fix the siting plan so the next routine is not at that hose bib.
The repeats were all negative. Does that invalidate the original?
No. 141.853(c)(1)(iii) says the state may not invalidate solely because the repeats are total coliform-negative. Clean repeats matter for the Level 1 trigger. They are not an automatic void.
What if the lab detected E. coli in the same bottle?
Treat it as the E. coli path until the state says otherwise in writing. Invalidation of a total coliform result is not a do-it-yourself pause on an acute MCL. Follow E. coli and total coliform violation response.
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Orevant provides compliance information tools. This page isn't legal advice. Confirm any invalidation request, replacement sample, and repeat set with your primacy agency.