Backflow Guidelines 732-240-2006
Two conditions create backflow. The first condition is backpressure; a greater pressure originating in the irrigation system can overcome the drinking water system supply pressure causing a reverse flow condition.
The second condition is backsiphonage; a suction created by the sudden loss of supply pressure, caused by water main breaks, and large demands such as fire fighting requirements.
Backpressure and backsiphonage can occur seperately or together. Different backflow preventers are designed to protect against one or both of these conditions.
RPZ - Reduced Pressure Zone Backflow Assembly
- Only one RPZ required to serve the whole system; (on/off valves can be located downstream of the RPZ)
- RPZ's must be installed a minimum of 12" above ground level.
- RPZ's must be tested by a State-certified Backflow Assembly Tester annually or when moved/repaired.
- In an RPZ equipped system, fertilizer and other agricultural chemicals may be introduced downstream of (after) the RPZ.
- Anti-siphon, anti-backpressure, multi-zone.
- May be installed in hilly terrain.
PVB - Pressure Vacuum Breaker
- Only one PVB required to protect the whole system; (on/off valves) can be located downstream of the PVB.
- PVB's must be installed a minimum of 12" above the highest point of water in the ystem.
- VB's must be tested by a State-certified Backflow Assembly Tester annually or when moved/repaired.
- No chemical or fertilizer can be introduced into an irrigation system protected by PVB's.
- No pumps or sources for backpressure on downstream side of (after) a PVB.
- Anti-siphon, multi-zone.
- Can be pressurized for a full 24 hours.
- Freeze resistant with "FR" feature.
AVB - Atmospheric Vacuum Breaker
- One AVB required for each irrigation zone; no (on/off valves) allowed downstream of the AVB.
- Each AVB must be installed a minimum of 6" above the highest point of water in the zone it protects.
- No chemical or fertilizer can be introduced into an irrigation system protected with AVB's.
- No pumps or sources for backpressure on downstream side of an AVB.
- Anti-siphon, single zone.
- Can be only pressurized for a maximum of a 12 hour period out of 24 hours.