A total coliform positive, worked from the phone call to the all clear

You get the call from the lab, not from your own test bench: a routine sample came back positive for total coliform. The clock did not start when you found out about it in the office. It started the moment the lab told you, and that timestamp now drives every deadline ahead of you.

A single coliform hit is not automatically a violation, and it does not automatically mean your water is unsafe. It means something is signaling, and the rule wants you to go find out what. Triggering an assessment is not a violation; failing to do it is.

The Revised Total Coliform Rule (RTCR) built the process around three moves: repeat sampling to confirm the signal, an assessment to find the cause, and a fix you write down. This walks the drill in order: what to sample in the first 24 hours, when an assessment gets triggered and by whom, what actually violates the E. coli limit, and the clock you are working against at each step.

What do you sample in the first 24 hours?

Within 24 hours of learning a routine sample was total coliform-positive, you collect and test at least three repeat samples:

• One from the same tap as the original sample.
• One from within five service connections upstream.
• One from within five service connections downstream.
• A fourth repeat sample if you collect one routine sample a month or less.

A single-connection system can spread the three repeats over three days instead of one, or fill a single container of at least 300 mL to cover the requirement in one draw.

The lab tests the original positive culture for E. coli. It also tests every positive repeat for E. coli, and that second test decides how serious this gets. If you are on quarterly or annual monitoring, a positive also adds three routine samples to the following month you serve water to the public.

What triggers a Level 1 assessment?

Two things trigger a Level 1 assessment: a system taking fewer than 40 samples a month that gets two or more total coliform-positive results in one month, or any system that fails to collect all of its required repeat samples. It is a self-assessment, meaning you or your operator does it, not an outside reviewer.

Once triggered, you have 30 days to complete the assessment and submit the form to your state. List every sanitary defect you found and the corrective action you took or scheduled.

What triggers a Level 2 assessment, and who does it?

A state-approved party does a Level 2 assessment, not your own staff, triggered by any of three things:

• An E. coli MCL violation.
• A second Level 1 trigger inside a rolling 12 months.
• For systems on reduced annual monitoring, a Level 1 trigger in two consecutive years.

The 30-day clock and the submission form work the same as Level 1. What changes is the depth of the review.

What actually counts as an E. coli MCL violation?

The E. coli MCL is violated by any one of four conditions, not just a bad lab result by itself:

• An E. coli-positive repeat sample after a total coliform-positive routine sample.
• A total coliform-positive repeat sample after an E. coli-positive routine sample.
• Failure to collect all required repeat samples after an E. coli-positive routine.
• Failure to test a total coliform-positive repeat for E. coli.

Two of the four are about paperwork and timing as much as biology. Missing a repeat sample or skipping the E. coli test can put you in violation even if the water turns out fine.

What does find and fix actually mean?

A sanitary defect is a pathway contamination can travel through, or a barrier close to failing. A missing well seal, a hole in a pipe, an unscreened tank vent are the textbook examples. The assessment exists to make you walk the system and find that pathway, not just retest until the number goes away on its own.

Corrective action has to match the cause you found, not repeat something generic because it worked last time. The options include:

• Disinfection or shock chlorination.
• Flushing until a measured residual returns, not until the water looks clear.
• Repairing the leaking pipe or valve.
• Holding system pressure between 35 and 100 psi, with at least 20 psi at the service connection.
• A cross-connection control program.
• Tank repair.
• Sampler training.
• Added monitoring or control.

Pick the one that addresses what you actually found in the system, and write it down with a schedule for anything not finished yet.

What is the corrective clock, day by day?

Every step in this drill runs against its own deadline. You get 24 hours to collect repeat samples after a positive routine result. You get 30 days from a Level 1 or Level 2 trigger to complete the assessment and submit the form.

If your source is ground water and you do not already provide 4-log virus treatment, a coliform positive in distribution adds one more obligation. You collect a Ground Water Rule source sample from each well within 24 hours, tested for a fecal indicator such as E. coli, enterococci, or coliphage, whichever your state specifies.

If that source sample comes back fecal-positive, you collect five more samples from the same source within 24 hours. A positive among those five, or a state directive, requires corrective action. The fix is one of four options:

• Eliminate the contamination source.
• Fix the deficiency.
• Switch to an alternate source.
• Add treatment that delivers 4-log virus inactivation before the first customer.

You consult your state on the fix within 30 days, and complete it within 120 days or on whatever schedule your state approves.

When does E. coli change everything?

An E. coli-positive result, whether in a routine sample or a repeat, moves you out of signal territory and into confirmed risk. It triggers a Level 2 assessment done by someone outside your own staff.

It also triggers a Tier 1 public notice: you tell the public within 24 hours, and you tell the state within 24 hours too. A fecal-positive source sample under the Ground Water Rule carries that same 24-hour Tier 1 notice.

Missing an assessment or corrective action deadline is a different kind of failure, a treatment technique violation, and it carries a Tier 2 notice instead: within 30 days, repeated every three months until it is resolved. The distinction matters for how you spend the first hour after the phone rings.

A confirmed E. coli hit means public notice today. A missed paperwork deadline means public notice this month.

Reduced monitoring is not a right; it is something your compliance history earns. Quarterly or annual sampling instead of monthly is only available if your state allows it, and only if you have a clean compliance history of at least 12 months, a sanitary survey or site visit showing no defects, and a protected source. A violation resets that clock too: it puts you back on monthly monitoring.

Your sample siting plan and last sanitary survey decide how often you will ever run this drill. See sanitary-survey-prep for the inspection that catches defects before a lab result does. If a positive tips into a public boil-water notice, boil-water-notice-and-crisis-comms covers that half of the clock, and sampling-monitoring-lab covers how the samples get collected and handled correctly in the first place.