Pressure Vacuum Breaker Assembly (PVB)
The standard backflow preventer for commercial irrigation systems without chemical injection. Protects against back-siphonage by introducing air when supply pressure drops. Must be installed above the highest downstream outlet.
Technical Specification
- CSA Standard
CSA B64.1.2— Pressure Vacuum Breaker Assemblies- Also listed as
- ASSE 1020 (US)
- Protection Type
- Back-siphonage only (not suitable for backpressure protection)
- Hazard Classification
- Minor hazard; irrigation without chemical injection
- Critical Installation Requirement
- Must be installed at least 150mm (6 inches) above the highest downstream outlet or overflow point
- Testing Frequency
- Annual
- Seasonal Note
- Must be winterized (drained) before freezing temperatures; reassembled and retested in spring
CSA B64.1.2 — Canadian Standards Association; ASSE 1020 — American Society of Sanitary Engineering
How the PVB Works
The PVB contains two components operating together:
- Spring-loaded check valve — Prevents reverse flow under normal backpressure conditions
- Air inlet valve (vacuum breaker) — Opens when supply pressure drops below atmospheric pressure (back-siphonage condition), introducing air to break the vacuum and prevent siphoning of downstream contaminants back into the supply
Important limitation: The PVB protects against back-siphonage only. It cannot be used where backpressure could occur (i.e., where downstream pressure might exceed supply pressure). For this reason, PVBs cannot be installed downstream of booster pumps or where the downstream system is pressurized independently.
Applications
- Commercial irrigation systems (without chemical injection) — Golf courses, athletic fields, landscaping systems, commercial properties
- Hose bibb connections — Outdoor service connections on commercial properties
- Utility/janitor room connections — Mop sink fill valves where back-siphonage is the primary concern
Not acceptable for: Irrigation systems with chemical injection (fertilizer, herbicide, pesticide), underground irrigation (where the valve cannot be installed above the highest head), any application where downstream backpressure can exceed supply pressure.
PVB vs. SVB vs. RPZ for Irrigation
| Assembly | Backpressure Protection | Chemical Injection OK | Indoor Install | Below Grade |
|---|---|---|---|---|
| PVB (CSA B64.1.2) | No | No | Conditional | No |
| SVB (CSA B64.1.3) | No | No | Yes (spill-resistant) | No |
| RPZ (CSA B64.4) | Yes | Yes | Yes (drain required) | No (relief valve) |
Frequently Asked Questions — PVB
Does a PVB need to be tested annually?
Yes. All approved backflow prevention assemblies — including PVBs — must be tested annually by a certified tester under most Canadian municipal water authority bylaws. The field test verifies that the check valve holds and the air inlet valve opens at the correct vacuum level.
Can a PVB be used indoors?
The standard PVB (CSA B64.1.2) discharges water from the air inlet valve during normal operation cycling, which makes indoor installations messy. The Spill-Resistant Vacuum Breaker (SVB, CSA B64.1.3) is the indoor-appropriate version. Some water authorities accept SVBs in place of PVBs for indoor installations.
Does my irrigation system need a PVB or an RPZ?
If your irrigation system uses chemical injection (fertilizer, pesticide, herbicide injectors), an RPZ is required — the connection becomes severe-hazard. If it is a clean water system without chemical injection and the PVB can be installed above the highest sprinkler head, a PVB may be acceptable. The water authority makes the classification. When in doubt, specify an RPZ.
Need your PVB tested this season?
We test irrigation system backflow preventers across Canada.