If your community has its own well, or its own distribution lines behind a master meter, there is a reasonable chance you are the legally responsible operator of a public water system and do not think of yourself that way.

The threshold is low. Fifteen service connections, or twenty-five people served on average sixty days a year. Not both — either. A fifteen-pad community with its own well crosses it. So does a community serving twenty-five residents through any constructed conveyance.

Once across, you are not a landlord who happens to supply water. You are a water utility, with monitoring schedules, an annual report you must mail to every resident by 1 July, public notification deadlines measured in hours, and a certified operator requirement. Federal civil penalties run to $71,545 per day per violation.

The Associated Press analysed EPA data in 2025 and found that nearly 70% of manufactured housing communities running their own water systems had violated safe drinking water rules over the previous five years, against 48% for cities. More than half had failed to perform a required test for at least one contaminant, or failed to report the results properly.

That is not primarily a story about bad water. It is a story about operators who did not know they were utilities.

This guide covers regulatory compliance of the water system itself. How you charge residents for water — RUBS, submetering, billing method — is a separate subject and a separate article.

General information, not legal or engineering advice. Drinking water regulation is enforced by state primacy agencies whose rules can exceed the federal floor.

Key takeaways

• The trigger is 15 service connections OR 25 people served at least 60 days a year — either one, not both.
• A year-round community with its own source is a community water system, the most heavily regulated category.
• Consumer Confidence Reports are due by 1 July every year, and the revised rule requirements start in 2027.
• Public notification for the most serious violations is 24 hours.
• Lead and Copper Rule Improvements deadlines are live: baseline inventory by 1 November 2027, monitoring from 1 January 2028, action level cut from 0.015 to 0.010 mg/L.
• Federal penalties reach $71,545 per day per violation; Colorado adds up to $10,000 plus $5,000 per continuing month.
• Persistent failure can end in receivership — a court appointing someone else to run your water system.

When your community becomes a regulated water system

40 CFR §141.2 defines a public water system as one "for the provision to the public of water for human consumption through pipes or, after August 5, 1998, other constructed conveyances, if such system has at least fifteen service connections or regularly serves an average of at least twenty-five individuals daily at least 60 days out of the year."

The word doing the work is or.

From there, three categories:

Almost every year-round manufactured housing community with its own well is a community water system — the category that attracts the full regulatory suite: all maximum contaminant levels, Consumer Confidence Reports, lead and copper, disinfection byproducts.

The ambiguous case is a community that buys treated water from a municipality but owns and maintains the distribution lines behind the meter. Most states do not regulate those as separate public water systems. Utah is a documented exception. If that describes you, get the answer from your state primacy agency in writing rather than assuming — the difference is the entire compliance programme.

What compliance actually requires

Microbial monitoring- For a community water system serving 1,000 or fewer people on groundwater, 40 CFR §141.855 sets the routine frequency at "one sample/month." Reduced quarterly monitoring is available but conditional — you need compliance with state certified-operator provisions, "a clean compliance history for a minimum of 12 months," a sanitary survey showing the system "free of sanitary defects," and one further safeguard. A total coliform failure triggers a Level 1 or Level 2 assessment, and any sanitary defect identified must be corrected.

Note the compounding: an operator without a certified operator cannot qualify for reduced monitoring, so the shortcut costs you four times the sampling.

The annual report- 40 CFR §141.155 requires that "each community water system must distribute reports by July 1 each year." Systems serving more than 10,000 distribute twice yearly; smaller systems keep the single annual delivery. The revised Consumer Confidence Report rule takes effect for reports from 2027.

Public notification. Subpart Q sets three tiers, and the top one is brutal:

Reporting to the state. Sampling results are due within the first ten days following the month the result is received. Violations must be reported within 48 hours. After issuing a public notice you must certify compliance and provide a copy within ten days.

A certified operator. Required for community and non-transient non-community systems, administered by state programmes. EPA enforces state adoption by withholding 20% of a state's Drinking Water State Revolving Fund capitalisation grant if it lacks a programme.

The lead deadlines are live

This is the compliance item most likely to catch an operator out in the next eighteen months, because the deadlines are near and the work is slow.

EPA's Lead and Copper Rule Improvements require every system, regardless of size, to:

• Have developed an initial service line inventory by 16 October 2024
• Complete a baseline inventory by 1 November 2027
• Begin standard six-month monitoring from 1 January 2028 where lead or galvanised-requiring-replacement lines exist
• Meet a lead action level cut from 0.015 mg/L to 0.010 mg/L
• Replace lead and GRR service lines within ten years or less

Systems serving 50,000 or fewer can qualify for triennial monitoring after three consecutive years below the action level — but the inventory obligation has no small-system exemption.

One honest caveat. The rule is under legal challenge. As of April 2026 briefing in the case was complete with oral argument expected in autumn 2026. We found no documented stay and no announced deadline extension, so treat the deadlines as live. A community that has not started its service line inventory is already past the first one.

States that go further

The federal rules are a floor. Some states have built specifically on manufactured housing.

Colorado is the most aggressive in the country. Its statute requires the state health department to develop a specific sampling and testing plan for each community, with baseline parameters at entry points and in distribution covering pH, TDS, iron, manganese, colour, odour, hardness, calcium, sulfate, fluoride and chloride. Communities not classified as public water systems must additionally test total coliform with chlorine residual, disinfection byproducts, and lead and copper across five samples. PFAS testing applies to every community.

Colorado also imposes owner duties that go beyond testing: notify residents within five days "in the language chosen by the residents," submit a remediation plan within 120 days, complete remediation on an approved schedule, and — the one with real financial consequence — not impose the cost of compliance on residents. Penalties run to $10,000 plus an additional $5,000 for each full calendar month the violation continues, with separate penalties for retaliatory eviction over a water complaint.

Florida requires each community's water supply to comply with the state's drinking water rules, and mandates at least one service connection per space designed "to prevent backflow or back-siphonage," with the system "designed for the maximum water demand."

Minnesota maintains park-specific water supply and sewage disposal rules alongside an operator licensing regime.

Whether your state layers anything on the federal floor is a per-state question — the landscape is indexed in the 50-state operator's index.

Wells, septic and the obligations nobody expects

Your septic system may be a federally regulated injection well. EPA classifies a large capacity septic system as one that "receives solely sanitary waste either from multiple dwellings or from a non-residential establishment and the system has the capacity to serve 20 or more persons per day." That makes it a Class V well under the Underground Injection Control programme, requiring inventory information — facility name, location, owner and operator contact, well type, operating status — filed with the permitting authority.

This is not theoretical. A 2025 federal consent decree involving a manufactured housing community included, among its claims, failure to provide Class V injection well inventory information. Most operators with a community septic system have never filed anything.

Discharging treated wastewater requires an NPDES permit or the state equivalent, and wastewater operator certification is a separate credential from drinking water certification, run by separate state programmes.

On-site wells carry their own permitting. In some states a well serving a public water supply requires both a construction permit before work starts and a separate permit to operate before use.

What violations actually cost

Federal civil penalties, inflation-adjusted as of January 2025 under 40 CFR §19.4:

These accrue per violation per day, which is why a monitoring lapse across several contaminants compounds faster than operators expect.

Enforcement is real and recent. In April 2024, EPA announced it had investigated 20 manufactured housing communities serving roughly 920 residents in one region, finding arsenic above the 10 ppb federal limit and seven communities with no regulated arsenic treatment in place. Emergency administrative orders went to nine communities; point-of-use arsenic treatment was installed in over 220 homes.

One of those matters settled by consent decree in January 2025 with a $50,000 civil penalty — but the penalty was the cheap part. The injunctive relief ran two years and required treatment system alarms, at least 80,000 gallons of additional storage, a booster pump, operators on site seven days a week until alarms were installed, agency-assisted standard operating procedures, quarterly compliance meetings, 24-hour violation notification, and a wastewater system assessment.

And you can lose control entirely. Washington's health department describes a receiver as "an entity appointed by the court to manage a water system" — used after informal action and formal orders have failed. The state attorney general petitions, naming a recommended receiver. The owner regains control only with the agency's approval, and the court may impose conditions including bonding, financial audits, certified operators and financial viability standards. Emergency appointment can happen in three days with a full hearing within fourteen. Comparable authority exists in Texas and Connecticut.

The scale of the problem, and why nobody knows it

The AP's 2025 analysis of EPA data found that nearly 70% of manufactured housing communities running their own water systems violated safe drinking water rules over five years, against 48% for cities and 57% for larger towns. More than half failed to perform a required test for at least one contaminant or failed to report results properly, and communities were far more likely to be repeat offenders. Methodology matters: EPA data through Q1 2025, compared against small systems serving 500 or fewer people, excluding systems serving fewer than 25.

There is no reliable national count of how many communities run their own water systems, and the reason is instructive. Utah's initial database search identified only four small systems as belonging to manufactured housing communities; keyword searching found 33 more. Colorado identified 79 communities with unknown water sources only after passing new testing requirements.

The regulator frequently does not know who the regulated systems are. If you have never had a conversation with your state primacy agency about your system, do not read that as absence of obligation — read it as absence of discovery.

The compliance file you need

Everything above reduces to a records question, and the file has to be current, not reconstructable:

• Your system classification in writing from the state primacy agency, and the basis for it
• Connection and population counts, which is what determines classification and can change with occupancy
• The monitoring schedule and every result, with the date received and the date reported
• Certified operator credentials and renewal dates
• CCR distribution evidence for each 1 July
• Every public notice, with tier, trigger date, issue date and the certification filed
• The service line inventory, with the 2027 baseline deadline tracked
• Class V well inventory filing if you have a community septic system
• Sanitary survey findings and the correction of every identified defect

Missing any of these is itself a violation in most cases, independent of whether the water was ever unsafe. That is the central point about SDWA enforcement — the AP finding was not that most communities have contaminated water. It was that most have monitoring and reporting failures.

How RIOO fits

RIOO is a property management platform built natively on Oracle NetSuite, and the community — not just the homesites within it — is a record that carries its own attributes.

Water system classification, connection counts, certified operator credentials and renewal dates, monitoring schedules, and notification and reporting deadlines live on the property record with dates attached, so a 1 July report or a certification renewal surfaces as a task rather than as an enforcement letter. Because connection counts derive from occupied homesites in the same system, a change in occupancy that affects your classification is visible rather than buried.

Compliance capital — treatment, storage, line replacement — sits against the property in the same NetSuite ledger as the revenue, which is what turns a service line replacement programme into something you can budget across a portfolio.

See how RIOO handles manufactured housing communities.

Conclusion

Fifteen connections or twenty-five people. That is the line between being a landlord who supplies water and being a regulated water utility, and a great many operators are on the far side of it without having noticed.

The evidence suggests this is the norm rather than the exception: roughly seven in ten communities running their own systems have violated the rules, mostly through monitoring and reporting failures rather than contamination. Regulators frequently cannot identify which systems exist. The lead service line deadlines arrive in 2027 and 2028 regardless.

Three things are worth doing this quarter. Confirm your classification in writing with your state agency. Start the service line inventory if you have not. And find out whether your community septic system is a Class V injection well that should have been inventoried years ago.

None of it is difficult. All of it is expensive to have skipped.

Frequently asked questions

Q1. When does a mobile home park become a public water system?
When it has at least 15 service connections or regularly serves an average of at least 25 individuals daily for at least 60 days a year. Either threshold alone is enough. A year-round community with its own source is generally a community water system.

Q2. What if we buy water from the city but own the pipes?
Most states do not regulate that as a separate public water system, but Utah does, and interpretations vary. Get your classification confirmed in writing by your state primacy agency rather than assuming.

Q3. What are the main compliance obligations?
Routine monitoring (monthly coliform sampling for small groundwater systems), a Consumer Confidence Report distributed by 1 July each year, tiered public notification with a 24-hour deadline for the most serious violations, 48-hour violation reporting to the state, and a certified operator.

Q4. When are the lead service line deadlines?
Initial inventory was due 16 October 2024; the baseline inventory is due 1 November 2027; six-month monitoring begins 1 January 2028 for systems with lead or galvanised-requiring-replacement lines. The action level drops from 0.015 to 0.010 mg/L, and replacement must complete within ten years.

Q5. What are the penalties?
Federal civil penalties reach $71,545 per day per violation. States add their own — Colorado authorises up to $10,000 plus $5,000 for each continuing month. Injunctive relief in a consent decree typically costs far more than the penalty.

Q6. Can we lose control of our water system?
Yes. Where informal action and formal orders fail, a court can appoint a receiver to manage the system. In Washington, emergency appointment can occur within three days, and the owner regains control only with agency approval.

Q7. Is our community septic system regulated?
Possibly as a Class V injection well. A large capacity septic system receiving solely sanitary waste from multiple dwellings with capacity to serve 20 or more persons per day is a Class V well requiring inventory information filed with the permitting authority. A 2025 federal consent decree included a failure-to-inventory claim.