How to Schedule RTCR Repeat Samples

A total coliform-positive routine starts a repeat set, not a debate about next month. 40 CFR 141.858 says you collect a set of repeat samples within 24 hours of being notified of the positive result, unless the state extends that window in writing. For each total coliform-positive routine, you collect no fewer than three repeats. That is a different job from the monthly routine count.

This page is how to schedule those repeats: how many, which taps, what the 24-hour clock actually means, and what happens if you miss one. Routine frequency lives on Total coliform sampling frequency under the RTCR. Where the taps belong lives on Coliform sample siting plan requirements. Confirm the sites and any extension with your primacy agency. Wyoming, the District of Columbia, and tribal systems ask the EPA region with primacy. This isn't legal advice.

Repeats are not extra routines

Routines are the samples your population and source type already owe. Repeats are the set you take because a routine came back total coliform-positive. You do not skip next month's routine because you just took repeats, and you do not wait for the next scheduled routine day to "catch" the positive. The repeat clock starts when the lab notifies you. Write the original collection time, the notification time, the 24-hour deadline, and each repeat time on one line. Put the PWSID and the original sample number on every chain of custody. If you need the identifier, use PWSID lookup.

How many repeats, and where they go

141.858(a)(1) and (a)(2) set the count: a set of repeat samples within 24 hours, and no fewer than three repeat samples for each total coliform-positive sample found. Small systems that take one routine a month still take three repeats after that one positive. Systems that take more than one routine a month still take three repeats for each positive routine. The state can require more. It cannot let you take two and call it a set.

141.858(a)(5) places those three bottles unless the state has approved a different layout in your siting plan:

• One at the original tap where the total coliform-positive routine was taken.
• One within five service connections upstream of that tap.
• One within five service connections downstream of that tap.

If the original tap sits at the end of the distribution system, or one connection from the end, the state may waive the upstream or the downstream bottle. Ask. Do not skip an end-of-line bottle on your own. If the system has a single service connection, 141.858(a)(4) lets the state allow the three repeats over a three-day period, or a larger-volume repeat whose total volume is at least 300 ml. That alternative is a state permission, not a default.

The siting plan is supposed to name these repeat locations before the lab calls. If the plan is silent, collect the three bottles as the rule describes and fix the plan after the set is in the cooler. Do not delay the 24-hour set to rewrite the plan.

The 24-hour clock, and the only way it moves

The clock starts when you are notified of the total coliform-positive result. Notification is the lab call, the lab email, or the result posting the lab uses, not the day you happen to read it. If the lab left a voicemail at 4:00 p.m. and you hear it at 8:00 the next morning, you are already on the clock. Check results the day they are due.

The state may extend the 24-hour limit on a case-by-case basis if the system has a logistical problem beyond its control. The state must specify how much time you have. A closed road or a lab that cannot kit bottles until morning are usual asks. "The board meets Thursday" is not.

Ask for the extension before the 24 hours run out. Get it in writing. A verbal "that's fine" is not an extension. Put the new deadline on the same line as the original notification time. Collect all required repeats on the same day unless the state has given you the single-connection alternative. 141.858(a)(4) is the same-day rule. Spreading the three bottles across a week because it is convenient is a miss.

Use a state-certified drinking-water lab and the same method the routine used: How to choose a state-certified drinking water lab.

What a missed repeat does

For the small systems that take fewer than 40 total coliform samples a month, 40 CFR 141.859(a)(1) names failure to take every required repeat after any single total coliform-positive sample as a Level 1 trigger. You do not need a second positive. Missing the set is enough. The assessment is what you owe for the missing bottles, not a debate about whether the water was fine. See How to prepare for an RTCR Level 1 assessment.

A late bottle on day four, without a written extension, does not automatically cure the miss. Take it if the state wants it, and ask whether the Level 1 trigger still stands.

Two or more total coliform-positive samples in the same month is the other common Level 1 trigger for small systems. Routine plus repeats all count. One TC+ routine and a clean set of three repeats is not a Level 1. A second TC+ anywhere in that month, including in the repeat set, is. That is why the placement matters. An upstream or downstream positive is a distribution result, not a reason to throw out the original.

What else the same TC+ starts

The repeat set is not the only clock on a total coliform-positive routine.

• E. coli. The lab analyzes the total coliform-positive bottle for E. coli unless it already did. An E. coli-positive routine or repeat is an acute MCL path and a Level 2 path. See E. coli and total coliform violation response and How to prepare for an RTCR Level 2 assessment. Do not wait on the rest of the repeat set to start that path.
• Triggered source monitoring. A groundwater system still owes the Groundwater Rule source sample, usually within 24 hours of the same notification. That bottle is from the well, not from the three distribution repeats. See Groundwater Rule triggered source water monitoring.
• Invalidation. If you think the original bottle was a lab error or a bad tap, you may ask the state to invalidate it. You still collect the repeats while that request is pending. Invalidation is a different page and a state decision, not an operator pause.

Keep the original result, the three repeat chains of custody, the lab reports, any extension email, and the siting-plan page that named the taps. Coliform records stay on file for five years under 40 CFR 141.33. See water system record retention.

The hour the lab calls: write the notification time, pull the siting plan, and collect all three repeats on the same day unless you have a written single-connection alternative. Label each bottle with the PWSID, the site ID, and the original sample number. If you cannot make the taps in 24 hours, ask for a written extension before the window closes. Do not cancel next month's routine.

FAQ

We take one routine a month. Do we still take three repeats?

Yes. 141.858 requires no fewer than three repeat samples for each total coliform-positive sample. The monthly routine count does not shrink the repeat set. See Total coliform sampling frequency under the RTCR for the routine table. This page is the repeat set after a positive.

What if I miss one of the three?

You have not taken every required repeat. For a small system that is a Level 1 trigger even if the two bottles you did collect are clean. Take the missing bottle if the state still wants it, and start the Level 1 path: How to prepare for an RTCR Level 1 assessment.

Check my system at /find-my-system.

Orevant provides compliance information tools. This page isn't legal advice. Confirm the repeat sites, the 24-hour clock or any extension, and the Level 1 trigger with your primacy agency.