Drinking water total coliform (RTCR) practice questions
20 free practice questions from 40 CFR Part 141 Subpart Y. Each answer is explained and linked to the rule it comes from.
Drinking water total coliform (RTCR)
20 questions across 8 topics. After each answer you see why it is right, with a link to the official source.
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General provisions and laboratory methods
1. What does 141.852(a)(2) require systems to determine about total coliforms and E. coli in a sample?
- A. Only their presence or absence; a determination of density is not required
- B. The most probable number per liter
- C. The density in colonies per 100 ml
- D. The density of E. coli only
Show answer
Answer: A. Only their presence or absence; a determination of density is not required
"Systems need only determine the presence or absence of total coliforms and E. coli; a determination of density is not required."
Source: eCFR: 40 CFR 141.852, Analytical methods and laboratory certification (as of Nov 3, 2026)
2. Footnote 4 to the method table in 141.852(a)(5) says exposure of filtration equipment to UV light is not adequate to ensure sterilization. Unless pre-sterilized disposable funnel units are used, how must every membrane filtration series begin?
- A. With equipment rinsed in sodium thiosulfate
- B. With equipment exposed to UV light for at least 2 minutes
- C. With membrane filtration equipment that has been sterilized by autoclaving
- D. With equipment wiped down with chlorine bleach
Show answer
Answer: C. With membrane filtration equipment that has been sterilized by autoclaving
"All filtration series must begin with membrane filtration equipment that has been sterilized by autoclaving. Exposure of filtration equipment to UV light is not adequate to ensure sterilization." UV may be used afterward only "to sanitize the funnels between filtrations within a filtration series."
Source: eCFR: 40 CFR 141.852, Analytical methods and laboratory certification (as of Nov 3, 2026)
Sample siting plans and sample validity
3. Under 141.853(a)(2), which systems may collect all required total coliform samples on a single day, if the samples are taken from different sites?
- A. Any community water system serving 10,000 or fewer people
- B. Systems that use only ground water and serve 4,900 or fewer people
- C. Systems serving more than 4,900 people that use surface water
- D. Subpart H systems serving 1,000 or fewer people
Show answer
Answer: B. Systems that use only ground water and serve 4,900 or fewer people
Samples go at regular intervals through the month, "except that systems that use only ground water and serve 4,900 or fewer people may collect all required samples on a single day if they are taken from different sites."
4. A system takes special purpose samples to check whether disinfection was sufficient after a main repair. How does 141.853(b) treat those samples?
- A. They must be included when calculating whether the coliform treatment technique trigger has been exceeded
- B. They must not be used to determine whether the coliform treatment technique trigger has been exceeded
- C. They count as repeat samples under 141.858
- D. They count toward the trigger only if they are total coliform-positive
Show answer
Answer: B. They must not be used to determine whether the coliform treatment technique trigger has been exceeded
Special purpose samples, "such as those taken to determine whether disinfection practices are sufficient following pipe placement, replacement, or repair, must not be used to determine whether the coliform treatment technique trigger has been exceeded."
5. Under 141.853(c)(1)(i), what may the laboratory establish that allows the State to invalidate a total coliform-positive sample?
- A. That all repeat samples are total coliform-negative
- B. That the system has only one service connection
- C. That the sample was collected on a weekend
- D. That improper sample analysis caused the total coliform-positive result
Show answer
Answer: D. That improper sample analysis caused the total coliform-positive result
The State may invalidate a total coliform-positive sample when "The laboratory establishes that improper sample analysis caused the total coliform-positive result." It "may not invalidate a total coliform-positive sample solely on the grounds that all repeat samples are total coliform-negative."
Non-community ground water systems serving 1,000 or fewer
6. What routine total coliform monitoring frequency does 141.854(b) set for a non-community water system serving 1,000 or fewer people using only ground water, when it is not a seasonal system and none of paragraphs (c) through (h) and (j) changes its schedule?
- A. Once every three years
- B. Each week that the system provides water to the public
- C. Each calendar quarter that the system provides water to the public
- D. Twice a month
Show answer
Answer: C. Each calendar quarter that the system provides water to the public
"Systems must monitor each calendar quarter that the system provides water to the public, except for seasonal systems or as provided under paragraphs (c) through (h) and (j) of this section."
7. A non-community ground water system serving 1,000 or fewer people is on annual monitoring and has one subpart Y monitoring violation, with no other listed event. What does 141.854(f) require?
- A. Begin quarterly monitoring the quarter following the event
- B. Stop serving water until a Level 2 assessment is completed
- C. Take one make-up sample and remain on annual monitoring
- D. Begin weekly monitoring the week following the event
Show answer
Answer: A. Begin quarterly monitoring the quarter following the event
Under 141.854(f), "A system on annual monitoring that experiences the event identified in paragraphs (f)(5) of this section must begin quarterly monitoring the quarter following the event"; (f)(5) is "one subpart Y monitoring violation for a system on annual monitoring."
Community ground water systems serving 1,000 or fewer
8. A community water system serving 1,000 or fewer people using only ground water is on reduced (quarterly) monitoring and loses its certified operator. What does 141.855(d)(1) require?
- A. Return to monthly monitoring after a rolling 12-month period
- B. Complete a Level 2 assessment within 30 days
- C. Stay on quarterly monitoring until the next sanitary survey
- D. Return to monthly monitoring the month following that loss
Show answer
Answer: D. Return to monthly monitoring the month following that loss
"A system that loses its certified operator must return to monthly monitoring the month following that loss."
9. What floor does 141.855(d)(1) set when the State reduces the monitoring frequency of a community water system serving 1,000 or fewer people using only ground water?
- A. No less than once every six years
- B. No less than annual monitoring
- C. No less than once every three years
- D. No less than quarterly monitoring
Show answer
Answer: D. No less than quarterly monitoring
"The State may reduce the monitoring frequency from monthly monitoring to no less than quarterly monitoring" if the system meets the listed criteria.
Subpart H systems and systems serving more than 1,000
10. Under 141.856(b), what routine total coliform monitoring frequency applies to a subpart H system serving 1,000 or fewer people, including a consecutive system?
- A. Monthly, with no reduction allowed
- B. Annually, after a State site visit equivalent to a Level 2 assessment
- C. Quarterly, if it is in compliance with State-certified operator provisions
- D. Quarterly, once it has a clean compliance history for 12 months
Show answer
Answer: A. Monthly, with no reduction allowed
"Subpart H systems of this part (including consecutive systems) must monitor monthly. Systems may not reduce monitoring."
11. Under 141.857(c), what must a subpart H system serving more than 1,000 people that does not practice filtration in compliance with subparts H, P, T and W do on each day its source water turbidity (measured as specified in 141.74(b)(2)) exceeds 1 NTU?
- A. Collect three repeat samples at the entry point to the distribution system
- B. Double the number of routine samples for that month
- C. Collect at least one total coliform sample near the first service connection
- D. Collect a coliform sample at the farthest point of the distribution system
Show answer
Answer: C. Collect at least one total coliform sample near the first service connection
The system "must collect at least one total coliform sample near the first service connection each day the turbidity level of the source water, measured as specified in § 141.74(b)(2), exceeds 1 NTU."
12. 141.857(d) says systems serving more than 1,000 people may not reduce monitoring, with one exception. Which systems does that exception cover?
- A. Subpart H community water systems serving fewer than 3,300 people
- B. Non-community water systems using only ground water (not GWUDI) that serve 1,000 or fewer people in some months and more than 1,000 in other months
- C. Any community water system using only ground water
- D. Consecutive systems that buy all of their water from a wholesale system
Show answer
Answer: B. Non-community water systems using only ground water (not GWUDI) that serve 1,000 or fewer people in some months and more than 1,000 in other months
"Systems may not reduce monitoring, except for non-community water systems using only ground water (and not ground water under the direct influence of surface water) serving 1,000 or fewer people in some months and more than 1,000 persons in other months."
Repeat monitoring and E. coli testing
13. Under 141.858(a)(2), repeat samples are normally collected on the same day. What may the State allow a system with a single service connection to do instead?
- A. Collect the set over a three-day period, or collect a larger volume repeat sample(s) totaling at least 300 ml
- B. Skip repeat sampling if next month's routine sample is negative
- C. Collect a single 100 ml repeat sample
- D. Collect the set at any time within 30 days
Show answer
Answer: A. Collect the set over a three-day period, or collect a larger volume repeat sample(s) totaling at least 300 ml
"The State may allow a system with a single service connection to collect the required set of repeat samples over a three-day period or to collect a larger volume repeat sample(s) in one or more sample containers of any size, as long as the total volume collected is at least 300 ml." The State "cannot waive the requirement for a system to collect repeat samples".
Source: eCFR: 40 CFR 141.858, Repeat monitoring and E. coli requirements (as of Nov 3, 2026)
14. A system collects a routine sample and, before it learns the result, collects another routine sample from within five adjacent service connections. The first sample is then found to contain total coliforms. What does 141.858(a)(4) allow?
- A. The system may count the second sample as a repeat sample instead of as a routine sample
- B. The State must invalidate the first sample
- C. The second sample becomes a special purpose sample
- D. The system must discard the second sample
Show answer
Answer: A. The system may count the second sample as a repeat sample instead of as a routine sample
If the system "collects another routine sample(s) from within five adjacent service connections of the initial sample, and the initial sample, after analysis, is found to contain total coliforms, then the system may count the subsequent sample(s) as a repeat sample instead of as a routine sample."
Source: eCFR: 40 CFR 141.858, Repeat monitoring and E. coli requirements (as of Nov 3, 2026)
15. Under 141.858(b)(2), on what basis may the State allow a system, case by case, to forgo E. coli testing on a total coliform-positive sample?
- A. All repeat samples are total coliform-negative
- B. The system serves fewer than 25 people
- C. The system assumes that the total coliform-positive sample is E. coli-positive
- D. The sample was collected at the end of the distribution system
Show answer
Answer: C. The system assumes that the total coliform-positive sample is E. coli-positive
The State may allow a system "to forgo E. coli testing on a total coliform-positive sample if that system assumes that the total coliform-positive sample is E. coli-positive." The system must then notify the State as in (b)(1), and "the provisions of § 141.63(c) apply."
Source: eCFR: 40 CFR 141.858, Repeat monitoring and E. coli requirements (as of Nov 3, 2026)
Treatment technique triggers and assessments
16. Which item does 141.859(b)(2) list among the minimum elements the assessor must review when conducting a Level 1 or Level 2 assessment?
- A. The system's water rates and billing records
- B. The operators' certification exam scores
- C. Sample sites, sampling protocol and sample processing
- D. The system's public notification history under subpart Q
Show answer
Answer: C. Sample sites, sampling protocol and sample processing
The assessor evaluates "minimum elements that include review and identification of inadequacies in sample sites; sampling protocol; sample processing", along with atypical events, distribution system changes, source and treatment considerations and "existing water quality monitoring data."
17. For a system with approved annual monitoring, which pattern does 141.859(a)(2) list as a Level 2 treatment technique trigger?
- A. Submitting a monthly monitoring report late
- B. One total coliform-positive sample in a year
- C. One missed annual routine sample
- D. A Level 1 trigger in two consecutive years
Show answer
Answer: D. A Level 1 trigger in two consecutive years
Level 2 triggers include, "For systems with approved annual monitoring, a Level 1 trigger in two consecutive years."
18. A completed assessment found sanitary defects that were not all corrected by the time the form was submitted. What does 141.859(c) require for the remaining corrections?
- A. Complete them within 24 hours of submitting the form
- B. Complete them on a timetable approved by the State in consultation with the system, and notify the State when each scheduled corrective action is completed
- C. Nothing further, because submitting the form ends the system's duties
- D. Repeat the full assessment every month until all defects are corrected
Show answer
Answer: B. Complete them on a timetable approved by the State in consultation with the system, and notify the State when each scheduled corrective action is completed
"For corrections not completed by the time of submission of the assessment form, the system must complete the corrective action(s) in compliance with a timetable approved by the State in consultation with the system. The system must notify the State when each scheduled corrective action is completed."
Violations, reporting and recordkeeping
19. Which situation does 141.860(a) list as a violation of the MCL for E. coli?
- A. The system has one total coliform-positive routine sample in which E. coli are not present
- B. The system fails to take every required routine sample in a compliance period
- C. The system fails to submit a completed assessment form after properly conducting the assessment
- D. The system fails to take all required repeat samples following an E. coli-positive routine sample
Show answer
Answer: D. The system fails to take all required repeat samples following an E. coli-positive routine sample
141.860(a)(3): "The system fails to take all required repeat samples following an E. coli-positive routine sample." Missing routine samples is a monitoring violation and a late assessment form is a reporting violation.
Source: eCFR: 40 CFR 141.860, Violations (as of Nov 3, 2026)
20. What deadline does 141.861(a)(4) set for a system to report a coliform monitoring violation to the State?
- A. By the end of the day the system discovers the violation
- B. Within 10 days after the system discovers the violation
- C. Within 48 hours after the system discovers the violation
- D. Within 90 days after the system discovers the violation
Show answer
Answer: B. Within 10 days after the system discovers the violation
A system that failed a coliform monitoring requirement "must report the monitoring violation to the State within 10 days after the system discovers the violation, and notify the public in accordance with subpart Q of this part."
Source: eCFR: 40 CFR 141.861, Reporting and recordkeeping (as of Nov 3, 2026)