Free checker · 40 CFR 141.2
Is my water system a public water system?
Enter connections and people served to see how the federal definitions classify your system: community, non-transient non-community, transient non-community, or not a public water system. Then see what that means day to day.
Start from an example
Community water systemWhat it means
Under the federal definitions
Community water systemCWS
- It has 40 service connections (15 or more).
- It serves an average of 90 people a day on 365 days a year (25 or more people, 60 or more days).
- 38 connections are used by year-round residents (15 or more).
What that usually means
- It needs a certified operator in responsible charge under your state's program.
- Ground water systems serving 1,000 or fewer people take a coliform sample every month; the state may reduce this to quarterly.
- If you add chlorine, the residual is measured at the same time and place as each coliform sample, and the running annual average must stay at or under 4.0 mg/L.
- A Consumer Confidence Report goes to customers every year by July 1.
- The state inspects the system (a sanitary survey) at least every three years, or five for systems that qualify.
Your state drinking water program makes the final call and can add requirements. Find your state program.
The federal definitions
A public water system provides water for human consumption through pipes (or other constructed conveyances) and has at least 15 service connections, or regularly serves an average of at least 25 people daily at least 60 days a year (40 CFR 141.2). Every public water system is one of three types:
| Type | Definition | Typical examples |
|---|---|---|
| Community (CWS) | At least 15 connections used by year-round residents, or at least 25 year-round residents | Mobile home parks, subdivisions, small towns, apartment complexes on their own well |
| Non-transient non-community (NTNC) | Not a CWS, but regularly serves at least 25 of the same people over six months a year | Schools, factories, office buildings and hospitals with their own water |
| Transient non-community (TNC) | Any other public water system: people don't stay long | Campgrounds, RV parks, gas stations, restaurants, churches open enough days |
The examples follow EPA's own descriptions (EPA: information about public water systems).
Counting connections and people
- Connections are each home, lot, site, building or business the system serves. Vacant lots with a service line may still count; ask your state.
- People means everyone the system serves: residents, employees, guests and customers. Average over the days you operate.
- States count in their own ways. Texas, for example, combines adjacent systems under common ownership, and counts connections for an RV park that buys its water as the number of sites divided by eight (30 TAC §290.38).
- Seasonal systems (open part of the year) still qualify on the 60-day test, and have their own start-up requirements.
What changes once you're a public water system
You'll have a system ID from the state, a sampling schedule, reports to file and records to keep. The day-to-day side is covered in two guides:
- Running a mobile home park water system (usually a community system)
- Campgrounds, RV parks and other transient systems
Every state's drinking water program is listed in the chlorine residual requirements guide.
Questions
Is a mobile home park a public water system?
Usually, if it supplies its own water. A park with 15 or more lots used by year-round residents, or 25 or more year-round residents, meets the federal definition of a community water system. Smaller parks can still fall under state rules.
Is a campground or RV park a public water system?
If it has 15 or more connections, or serves an average of 25 or more people a day on at least 60 days a year, yes. Because guests come and go, most are transient non-community systems. An RV park with many long-term residents can be a community system instead.
We buy our water from the city. Are we still a public water system?
Maybe not under federal rules. 40 CFR 141.3 exempts a system that only distributes and stores water bought from a regulated public system, doesn't treat it, doesn't sell it, and isn't an interstate passenger carrier. Whether billing residents for water counts as selling it is a question for your state.
Who decides?
Your state drinking water program (or EPA, in Wyoming and the District of Columbia). This checker applies the federal definitions; states can count connections differently or regulate smaller systems.
Sources
- 40 CFR 141.2 — Definitions (public, community, non-transient and transient water systems)
- 40 CFR 141.3 — Coverage (systems that only distribute purchased water)
- EPA — Information about public water systems
- 40 CFR 141.130 — Disinfectant residuals and byproducts: who the rule covers
- 40 CFR 141.132 — Monitoring requirements (residual with total coliform samples)
- 40 CFR 141.152 — Consumer Confidence Report deadlines
- 40 CFR 141.854 — Coliform monitoring for non-community ground water systems ≤1,000 people
- 40 CFR 141.855 — Coliform monitoring for community ground water systems ≤1,000 people
- 40 CFR 142.16(o) — Sanitary survey frequency for ground water systems
- EPA 816-R-00-022 — Operator certification guidelines: implementation guidance
- 30 TAC §290.38 — Texas definitions
- TCEQ RG-407 — How to complete the DLQOR (includes a mobile home park example)
Last reviewed September 28, 2026. Rules change and states add their own; confirm with your state drinking water program.