Short definition
WAC 246-290 is the WA Department of Health rule governing Group A public water systems — utilities serving 15+ connections or 25+ people for 60+ days per year. The rule covers design, operations, water quality, reporting, and (most relevantly for plumbing) cross-connection control under §246-290-490, which requires testable backflow assemblies on premises with cross-connection hazards and annual testing by a DOH-certified Backflow Assembly Tester.
What it is
WAC 246-290 is the WA implementation of the federal Safe Drinking Water Act for public water systems. It’s administered by WA DOH’s Office of Drinking Water. The rule covers everything a water utility must do — source protection, treatment, distribution-pressure minimums, monitoring, and reporting.
For plumbing work specifically, the rule’s most-cited section is:
- WAC 246-290-490 — Cross-Connection Control. Requires water purveyors (utilities) to establish a Cross-Connection Control program, identify cross-connection hazards on the premises they serve, and ensure backflow prevention assemblies are installed where needed and annually tested.
A cross-connection is any actual or potential physical connection between a potable water supply and a non-potable source. Backflow occurs when pressure differentials reverse flow, drawing contaminants into the potable supply. Common residential cross-connection hazards:
- Irrigation and lawn-sprinkler systems — contaminated by soil bacteria.
- Lawn-sprinkler with chemical injection — fertilizer or pesticide contamination.
- Fire sprinkler systems — stagnant water can support biofilm.
- Hose bibs — risk of submerged hose end siphoning contaminants (vacuum breaker required).
- Boiler / hydronic systems with chemical inhibitor — high-hazard cross-connection.
- Water softeners — typically lower-hazard but reviewed.
The rule requires testable assemblies on high-hazard installations: RPBA (reduced-pressure backflow assembly), DCVA (double-check valve assembly), PVB (pressure vacuum breaker), SVB (spill-resistant vacuum breaker). Annual testing by a DOH-certified Backflow Assembly Tester (BAT) is required, with results submitted to the water purveyor.
The companion rule under WAC 246-291 covers Group B systems — small private water systems serving 2–14 connections.
Why it matters to a homeowner
Three scenarios where homeowners encounter WAC 246-290 directly.
Lawn-sprinkler install. Adding a lawn-sprinkler system requires a testable backflow assembly (typically PVB or DCVA). After install, the assembly needs annual BAT testing. The water utility (SPU, Tacoma Water, Bellevue Utilities, etc.) sends an annual reminder; you have a defined window (typically 30 days) to schedule the test and submit results.
Boiler hydronic loop. A hydronic heating system with chemical inhibitor in the loop is a high-hazard cross-connection. The fill loop needs an RPBA at the water-supply tap. RPBA install and annual BAT test apply.
Hose bib upgrades. Each hose bib must have a vacuum breaker (ASSE 1011-listed). Modern frost-proof sillcocks include integrated vacuum breakers; older non-frost-proof hose bibs may need a screw-on vacuum breaker added. Not testable; no annual test required, but the device itself is mandatory.
When a contractor installs a backflow assembly, the work also typically requires a permit and a PL30-licensed installer. The plumber may hold both PL01/PL02 and PL30 + DOH BAT certifications, allowing them to install and test the assembly. If they don’t, they coordinate with a separate BAT for the annual test.
The cost of an annual BAT test runs roughly $50–$150 in WA. Skipping the test isn’t an option — the water utility tracks compliance and can shut off service for non-compliance.
When you’ll encounter this term
- An annual reminder letter from your water utility about backflow testing.
- A lawn-sprinkler install scope including a backflow assembly.
- A hydronic boiler install or replacement requiring an RPBA at the fill loop.
- A new construction permit referencing cross-connection control review.
Common variants and disambiguation
- WAC 246-290 vs. UPC §603 (cross-connection). WAC 246-290 governs the purveyor’s program (water utility’s responsibility). UPC §603 governs the plumbing installer’s responsibility (which assembly to install where). Both apply on a typical residential install.
- WAC 246-290 (Group A) vs. WAC 246-291 (Group B). Group A = public water systems. Group B = small private water systems (private well serving 2–14 connections). Different rules.
- BAT vs. PL30. BAT is the DOH testing certification. PL30 is L&I’s plumber-license type for backflow installation. Many WA plumbers hold both.
Washington note
WAC 246-290 is the bedrock WA drinking-water rule, administered by DOH’s Office of Drinking Water. The cross-connection control section (WAC 246-290-490) is the section that touches residential plumbing most directly.
For specific WA scenarios:
- Lawn-sprinkler new install: PVB or DCVA at the supply tap; annual BAT test.
- Existing irrigation without backflow: retrofit required if the utility identifies the hazard.
- Hydronic boiler with chemical inhibitor: RPBA at fill loop; annual BAT test.
- Hose bib without vacuum breaker: add a screw-on vacuum breaker or replace with a frost-proof sillcock that includes one.
The water utility is the enforcer for testing — they track which addresses have testable assemblies, send annual reminders, receive test results, and shut off service for non-compliance. Most WA utilities maintain online portals for BAT test result submission.
For BAT certification specifically, WA DOH administers the program. The certification is held individually (a person, not a company), and a plumber can be both PL30-licensed (install) and BAT-certified (test). Many WA plumbing companies offer both services.