Washington water billing rules for mobile-home parks (2026)

Washington's park water-billing law is genuinely short — two sections of the Manufactured/Mobile Home Landlord-Tenant Act do almost all the work. That surprises owners, because vendor websites describe a detailed statewide submetering statute with methodology disclosures and monthly-read mandates. Those describe bills that never passed. Here's what Washington law actually requires.

Part of our state-by-state series — submetered water billing rules by state. Other states: Texas · California · Florida · Oregon

Rule one: the lease discloses it (RCW 59.20.060)

The rental agreement must list the utilities and services available and the nature of any fees charged for them. And there's a built-in unbundling rule: if a utility that was part of rent becomes separately billed during the tenancy, the landlord must decrease rent proportionately. Unbundling is transparency, not a raise — same principle as Oregon and California, written in one sentence.

Rule two: actual cost, full stop (RCW 59.20.070(6))

It's a prohibited act for a park landlord to charge any tenant "a utility fee in excess of actual utility costs" — or to intentionally interrupt a tenant's utilities. No markup, no "convenience fee," no admin allowance like Texas's 9%. Washington's version of the no-markup rule is the strictest phrasing of the five big park states: your submetered water bills, in total, can't exceed what the utility charged you.

Does submetering make you a regulated utility? Usually not

Washington's utility commission (the UTC) regulates "water companies," but exempts small systems — under 100 customers with modest per-customer revenue. A typical 10-to-100-lot park reselling water to its own tenants at cost sits outside UTC regulation. Two cautions: the exemption has thresholds, so a large park should check its numbers, and cities can layer on local rules (Seattle has its own third-party utility billing ordinance). When in doubt, check the city before the state.

Common Washington mistakes

• Adding any fee on top of actual cost — even a small billing fee violates 59.20.070(6)
• Unbundling water from rent without the proportional rent decrease
• Following a "Washington RUBS statute" from a vendor site — the detailed statewide submetering bills (2004, 2011, 2019) all died; the codified rules are the two above
• Forgetting local ordinances, which can be stricter than the state

The billing math is the same as anywhere: reads in, at-cost bill out — the water submeter calculator does it in one step, and the state-by-state overview shows how Washington compares. Raising rent instead? Washington's new 5% cap has its own rules — see raising rent in a Washington mobile-home community.

Sources

• RCW 59.20.060 (rental agreement requirements): https://app.leg.wa.gov/rcw/default.aspx?cite=59.20.060
• RCW 59.20.070 (prohibited acts, incl. utility fees above actual cost): https://app.leg.wa.gov/rcw/default.aspx?cite=59.20.070
• RCW 80.04.010 (water company definition and small-system exemption): https://app.leg.wa.gov/rcw/default.aspx?cite=80.04.010
• WA Attorney General, Manufactured/Mobile Home Landlord-Tenant Act: https://www.atg.wa.gov/manufactured-mobile-home-landlord-tenant-act

General information, not legal advice. City ordinances can add requirements the state doesn't — confirm your city's rules before you change how you bill.