PVB & AVB Testing & Requirements
PVB test procedures, AVB inspection, installation requirements, continuous pressure rules, and height clearances.
- Perform the PVB test procedure including check valve and air inlet tests
- State the minimum installation height for PVB and AVB devices
- Explain the continuous pressure restriction for AVBs
- Identify when a PVB is appropriate vs when an RPZ or DCVA is needed
- Describe hose bib vacuum breaker requirements and applications
Lección 1
PVB Test Procedure & Installation Requirements
PVB Components
The Pressure Vacuum Breaker (PVB) contains two testable components:
- Check valve - a spring-loaded check that prevents backflow
- Air inlet - a valve that opens to admit atmospheric air when supply pressure drops, breaking any siphon condition
The PVB also has two test cocks and two shutoff valves.
PVB Test Procedure
The PVB test verifies both the check valve and the air inlet. Per ASSE/IAPMO/ANSI Series 5000-2022, the No. 2 shutoff valve must be fully closed before taking any differential pressure readings to establish a true no-flow (static) condition. Flow in the downstream line creates an artificial differential that produces false, inflated readings:
Check Valve Test:
- Close the No. 2 (downstream) shutoff valve - this is mandatory before any readings; flow creates false differential readings
- Connect hoses and bleed air
- Read the differential across the check valve
- The check valve must hold a minimum of 1.0 psi
Air Inlet Test:
- With the downstream shutoff closed, slowly open the test cock downstream of the check to reduce pressure on the downstream side
- As pressure drops, the air inlet should open and admit air
- The air inlet must open at 1.0 psi or less (when the pressure differential drops to 1.0 psi or below, the air inlet opens)
No-Flow State Is Required
ASSE mandates closing the No. 2 shutoff valve to confirm a no-flow state before taking differential pressure readings. Flow creates an artificial differential - the velocity head adds apparent pressure to the reading, producing a false pass result. Always confirm zero flow before recording any values.
Installation Requirements
PVB assemblies must be installed:
- At least 12 inches above the highest downstream point - this means 12 inches above the highest sprinkler head, outlet, or any point where water could exit the system
- In a vertical (upright) orientation - never horizontal, angled, or inverted
- Where they will not be subject to backpressure - no pumps or elevated tanks downstream
Height Is Critical
If a PVB is installed less than 12 inches above the highest downstream point, water can reach the air inlet and prevent it from functioning. The 12-inch minimum is a hard requirement - not a recommendation.
The PVB check valve must hold 1.0 psi minimum and the air inlet must open at 1.0 psi or less. The PVB must be installed at least 12 inches above the highest downstream point in a vertical orientation and is limited to backsiphonage-only protection.