RPZ vs. DCVA vs. PVB: what the assembly types protect against

An RP or RPZ assembly uses two checks and a relief valve and is commonly used where both backsiphonage and backpressure protection are needed, including high-hazard situations under many programs. A DCVA uses two checks and is commonly limited to lower-hazard applications. A PVB uses an air inlet to break a vacuum and protects against backsiphonage, not backpressure. An SVB is in the pressure-vacuum-breaker family and has the same backsiphonage-only boundary.

Those are functional descriptions, not an installation recommendation. Local codes, water-system policy, product approval, elevation, drainage, service conditions, and hazard classification can change what is allowed.

Sources for this section: EPA: Cross-Connection Control Manual; Washington Administrative Code: cross-connection control; California State Water Resources Control Board: Cross-Connection Control Policy Handbook (April 2026).

Sources for this section: EPA: Cross-Connection Control Manual; EPA: Protecting Water Quality through Cross-Connection Control and Backflow Prevention; USC Foundation: Field-test training tools; California State Water Resources Control Board: Cross-Connection Control Policy Handbook (April 2026).

• The protected service and the actual or potential contaminant source—not just the building type.
• Whether backpressure, backsiphonage, or both are credible at that point in the system.
• Whether the installation offers the required elevation, drainage, clearance, orientation, and access for the proposed assembly.
• The exact make, model, size, and approval listing the water system or authority accepts at the time of work.

Sources for this section: EPA: Cross-Connection Control Manual; USC Foundation: Approval Program; Washington Administrative Code: cross-connection control; California State Water Resources Control Board: Cross-Connection Control Policy Handbook (April 2026).

The assembly type determines the field-test procedure and the readings that belong on a record. An RP record includes relief-valve information; a DCVA record records both check valves; a PVB record addresses its air inlet and check. A form that uses the wrong reading set is not made correct by changing the label at the top.

The baseline math used by a tool may be useful for organizing a record, but only the receiving authority's accepted procedure and form determine whether a result is accepted. That is why the pages below stay separate instead of treating every assembly as one generic test.

Sources for this section: USC Foundation: Field-test training tools; Washington State Department of Health: Backflow prevention assembly field test report; Texas Commission on Environmental Quality: Cross-connection control and backflow prevention.

Product approval lists, local policies, and active code editions change. USC describes its own approval process and publishes information about approvals, but a USC listing is not a substitute for the model and policy accepted by the service's water system. Likewise, a state example can explain a rule structure but does not travel automatically to another state.

For a replacement, retain the decision source, permitted model information, installation approval, and the first test report in the same property record. That makes the next review less dependent on memory or a disconnected PDF.

Sources for this section: USC Foundation: Approval Program; Washington Administrative Code: cross-connection control; Texas Commission on Environmental Quality: Cross-connection control and backflow prevention.

This guide was reviewed on August 22, 2026. It links to primary public sources where possible and labels state and local examples as examples. It is educational material, not engineering, legal, installation, certification, or water-system approval advice.

• EPA: Protecting Water Quality through Cross-Connection Control and Backflow Prevention

  Definitions, assembly/device distinction, program elements, and incident-response context.

• EPA: Cross-Connection Control Manual

  Technical background on cross-connections, backpressure, backsiphonage, and mechanical protection.

• USC Foundation: Field-test training tools

  Current Foundation materials distinguish the RP, DC, PVB, and SVB field-test families.

• USC Foundation: Approval Program

  Explains USC laboratory plus one-year field-evaluation approval work for assemblies.

• ASSE International: Backflow Prevention personnel certification

  Current ASSE 5110 qualification requirements and the related cross-connection personnel certifications.

• ASSE International: Series 5000 professional qualifications standards

  Defines ASSE 5110 as a professional-qualifications standard, separate from assembly product standards.

• Washington Administrative Code: cross-connection control

  A state example for hazard assessment, approved protection, certified testing, repair, records, and annual scheduling—not a national rule.

• Washington State Department of Health: Backflow prevention assembly field test report

  An official example of report guidance; its required and optional fields are specific to Washington.

• Texas Commission on Environmental Quality: Cross-connection control and backflow prevention

  Shows that alternate forms and submission requirements are controlled by the receiving water system.

• California State Water Resources Control Board: Cross-Connection Control Policy Handbook (April 2026)

  A current statewide example of definitions, assembly limits, testing, repair, recordkeeping, and tester-recognition rules.

• Understand an RP / RPZ test reportSee the reading set associated with the reduced-pressure family.
• Understand a DCVA test sheetReview the two-check record separately from an RP.
• Understand a PVB inspection formSee the air-inlet and check information a PVB record needs.