Vacuum breakers, checks, and RP assemblies

Atmospheric vacuum breaker

An AVB uses an air inlet that opens when pressure falls, breaking a siphon. It protects against backsiphonage, not backpressure. Oregon OAR 333-061-0071 requires upright installation, no flooding, and at least six inches above the highest downstream piping and outlets. It is intermittent equipment and must not be pressurized more than twelve hours in any twenty-four-hour period.

Place an AVB downstream of the controlling valve and do not install a downstream shutoff that can leave it continuously pressurized. A conventional nozzle outlet does not mean every possible “restriction” is prohibited; the critical issue is an installation that defeats the device's approved operation. An AVB is non-testable in the assembly field-test sense. Visual inspection does not convert it into a certified double-check or reduced-pressure assembly.

Pressure vacuum breaker

A PVB adds a spring-loaded check and air inlet so it can operate under continuous pressure. It has shutoffs and test provisions. It protects against backsiphonage for permitted health and non-health hazards, but not against backpressure.

Oregon requires a minimum twelve inches above the highest downstream piping and outlets, protection from flooding, and room for maintenance and testing. A downstream valve may maintain pressure, but no pump or other means may impose backpressure. Adding an elevated outlet can make a previously adequate installation too low. Brief water discharge can occur during pressure changes, so choose a location where discharge is acceptable.

Spill-resistant vacuum breaker

An SVB limits startup spillage through its operating sequence. It is still a vacuum-breaker assembly: continuous-pressure operation is permitted, backsiphonage protection is provided, and backpressure protection is not. It does not guarantee that water can never escape.

The current Oregon rule applies the same twelve-inch elevation above downstream piping and outlets, no-flooding, no-backpressure, and access requirements to PVB and SVB installations. “Spill resistant” does not authorize hiding the assembly in a closet with no drainage or installing it below an uphill emitter. Check the exact listed model, orientation, and manufacturer instructions before installation.

Double Check Valve Assembly (DCVA — ASSE 1015)

The Double Check Valve Assembly (DCVA) is an in-line mechanical assembly featuring two independently acting, internally loaded (spring-assisted) check valves in series, flanked by two resilient-seated isolation shutoff valves and equipped with four test cocks.

Engineering and Hydraulic Operation

• The two independently acting checks provide redundant barriers. Their loading and test criteria are defined by the approved assembly and field-test procedure.
• A check's minimum differential-pressure test criterion is not a statement that its flowing pressure loss is always one psi. Total assembly loss varies with flow and must be taken from the manufacturer's performance data.
• A fouled or damaged check may fail to seal. Two checks and four test cocks do not eliminate the need for periodic qualified testing.

Oregon Regulatory Status: Low Hazard Only

• Backsiphonage and Backpressure: Fully approved to defend against both backsiphonage and backpressure.
• Continuous Pressure: Approved for continuous operating line pressure.
• Degree of Hazard Limitation: Under OAR 333-061-0070 and OPSC Section 603, a DCVA is approved strictly for Low Hazard (Non-Health Hazard) installations. For irrigation, assess chemical addition, auxiliary supplies, other contamination pathways, and the water supplier's required protection. A municipal connection without an injector does not automatically establish non-health-hazard status; use the actual hazard assessment.
• Below-Grade Vault Installation Permitted: Oregon permits a DC in a vault subject to installation conditions, including adequate drainage, protection from continuous submersion, and watertight fitted plugs or caps on test cocks. Do not connect the drain directly to a sanitary or storm sewer. Pea gravel alone does not prove adequate drainage. An RP has its own restricted drain-to-daylight vault exception, described below, so a DC is not categorically the only assembly ever permitted below grade.

Reduced-pressure principle assembly

An RP assembly has two independently acting checks and a differential relief valve between them. The intermediate zone is maintained below upstream pressure; the relief valve opens when the required differential is not maintained. It protects against permitted health and non-health hazards under both backsiphonage and backpressure.

Its relief discharge must remain open and protected from submersion. Never plug, extend, or directly connect the relief port to a closed drain. Provide the approved air-gap drainage arrangement capable of receiving the possible discharge. Current Oregon rules normally require horizontal installation unless the model is specifically approved for vertical installation, above the one-percent flood level unless the authority approves otherwise, and freeze protection when needed.

An enclosed vault or box is allowed only under the rule's bore-sighted, unrestricted drain-to-daylight conditions sized to prevent submersion. This is a specific exception, not unrestricted permission to bury an RP in a valve box. Above-ground installations are generally simpler to drain and service. Installations higher than five feet require a permanent OSHA-compliant service platform. Approved reduced clearances for pipes two inches or smaller still require authority approval and access.

Premises with irrigation chemical addition appear in Oregon's high-hazard table. Use the water supplier's required premises isolation and internal protection. An ordinary commercial address alone does not establish every assembly choice; actual hazards and authority requirements govern.

Selection matrix

The matrix screens hydraulic capability; it does not replace the water supplier's premises-isolation rules or the exact product listing. A PVB cannot solve a backpressure condition simply because its health-hazard capability is acceptable. A DC cannot solve a health-hazard condition simply because it handles backpressure.