Short definition
Backflow preventer is the umbrella term for any device that prevents reverse flow from a downstream connection into a potable supply. Specific types exist for specific hazard levels — from the simple hose-bib vacuum breaker on an outdoor sillcock to the reduced-pressure assembly (RPZ) protecting against high-hazard cross-connections at hospitals and chemical plants. WA DOH WAC 246-290-490 governs which device goes where.
What it is
The protection ladder, low hazard to high:
- Built-in fixture protection. Faucet aerators with anti-back design, toilet fill valves with built-in anti-siphon. Always present on code-compliant fixtures.
- HBVB (hose-bib vacuum breaker), ASSE 1011. Screws onto an outdoor hose-bib outlet. Back-siphonage protection only.
- PVB (pressure-vacuum breaker), ASSE 1020. Continuous-pressure low-hazard. Standard for irrigation systems. Back-siphonage only.
- DCVA (double-check valve assembly), ASSE 1015. Continuous-pressure low-hazard. Used on fire sprinklers, some irrigation. Protects against both back-pressure and back-siphonage at low-hazard tier.
- Dual check valve, ASSE 1024. Two checks in series, no test cocks. Used by some utilities at the meter as containment protection.
- RPZ / RPBA (reduced-pressure backflow assembly), ASSE 1013. High-hazard. Two checks plus a differential-pressure relief valve between them. Required for hospitals, chemical plants, photo labs, hydronic boilers, fire sprinklers with antifreeze, food processing, and similar high-hazard cross-connections.
- Air gap. Geometric protection — physical separation between outlet and flood rim. Highest possible protection; cannot be defeated mechanically.
The choice depends on hazard level and whether back-pressure is possible. Hazard determination is made by a certified Cross-Connection Specialist (CCS) under WA DOH guidance.
Why it matters to a homeowner
If you have any of these on your property, you have a backflow preventer:
- Irrigation system. Almost always a PVB or DCVA.
- Fire sprinkler system. Usually a DCVA on residential.
- Hydronic boiler. RPZ at the make-up line.
- Outdoor hose bibs. HBVB on each (modern frost-free sillcocks have one integrated).
- Pool fill connection. Air gap or RPZ depending on the install.
Annual testing is required on most approved assemblies (RPZ, DCVA, PVB) — the customer hires a BAT, pays for the test ($50–$150 typical), and the BAT submits results to the utility. Failed tests trigger repair or replacement followed by a retest.
The cost difference between assembly types is significant — an HBVB is $15, a PVB is $200–$400 plus install, an RPZ is $400–$2,500+ depending on size — and is matched to the hazard tier. Specifying a higher-tier device than required is fine but expensive; specifying a lower-tier device than required is a code violation.
Washington note
WA DOH WAC 246-290-490 is the regulatory backbone. Each WA water utility operates its own cross-connection program under that rule:
- Customer responsibilities. Install the right device at the right hazard, hire a BAT for installation and annual testing, submit documentation, repair or replace failed assemblies.
- Utility (purveyor) responsibilities. Operate the cross-connection control program, identify cross-connections through outreach and inspections, enforce annual testing, and may suspend service for non-compliance.
- Hazard determination. A certified Cross-Connection Specialist (CCS) classifies hazards as high or low and specifies the appropriate device class.
WA jurisdictions sometimes prefer DCVA over PVB on residential irrigation, or vice versa — local utility ordinance or program manual sets the choice. Confirm with your utility before specifying an irrigation backflow assembly.