What is a public water system?

If you own or manage a mobile home park, the phrase "public water system" comes up in lender questions, regulator letters, and operator conversations. This page explains the federal definition in plain language and shows why it matters for parks. It is general information — ParkWaterBinder does not determine your park's status. Confirm classification with your state primacy agency.

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The federal definition

Under the federal Safe Drinking Water Act, a Public Water System (PWS) is a system that provides water for human consumption through pipes or other constructed conveyances, where the system has at least 15 service connections or regularly serves at least 25 individuals. The 25-person threshold is generally measured as 25 or more people for 60 or more days a year. There are three statutory categories:

  • Community Water System (CWS). Serves the same people year-round — the category most mobile home parks with their own well fall into.
  • Non-Transient Non-Community (NTNC). Serves the same people, but not year-round (a school or office on a private well, for example).
  • Transient Non-Community (TNC). Serves transient users (a campground or rest stop).

The U.S. Environmental Protection Agency's information page on public water systems is a good starting reference; states publish their own implementing rules under primacy.

Why this matters for mobile home parks

Many parks meet the connection or population threshold without realizing it. A 30-home community on a single well will typically be classified as a Community Water System; the owner is then responsible for compliance monitoring, reporting, and resident notifications. Smaller parks — fewer than 15 connections and fewer than 25 residents — may fall outside the federal definition, but some states regulate "state small water systems" separately. Master-meter parks that resell municipal water sometimes are not the PWS themselves, but they still maintain distribution-side records.

Classification is fact-specific. The answer depends on connections, population, days served, and how water is delivered. Your state primacy agency — not ParkWaterBinder — is the right place to confirm.

Records park owners commonly keep

  • The park's PWS ID, if assigned, and the state-issued designation letter.
  • Source water description: well, surface water, purchased water, or a combination.
  • Sample schedules, lab reports, and chain-of-custody forms.
  • Resident notices and Consumer Confidence Reports (CCRs), with delivery proof.
  • Regulator correspondence, sanitary survey reports, and follow-up actions.
  • Resident complaints and the actions taken.

The full list lives in our public water system binder overview, and the park water-risk checklist is a free one-pager to get started.

Related reading

Bottom line

"Public water system" is a precise federal term, but for park owners the practical question is simpler: who is responsible for sampling, notification, and recordkeeping, and where do those records live? A binder — physical or digital — is the cheapest insurance an owner can buy. ParkWaterBinder makes that binder easier to build and easier to share when someone asks.

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ParkWaterBinder is not legal, engineering, or regulatory advice. Use it to organize records, identify missing evidence, and prepare questions for qualified professionals and regulators. ParkWaterBinder does not determine your park's PWS status — confirm with your state primacy agency.