A type of backflow preventer which seals off the atmospheric vent area when the system is pressurized. Should be installed downstream of a control valve in a location which is at least twelve inches higher than the highest point in the lateral which it serves. When system pressure drops to zero, the float and seal assembly drops, opening the vent to atmosphere and breaking any siphon effect. Consult local building codes or your Rain Bird distributor for laws applicable in your area. Synonymous with Atmospheric Vacuum Breaker.
(Simpler definition:) These anti-siphon devices are essentially one-way valves designed to stop the flow of potentially contaminated water back into the drinkable (potable) water supply. Anti-siphoning capabilities are required by code on certain plumbing devices, such as exterior faucets (sill-cocks) or utility sink faucets.
EXAMPLE:
Some anti-siphon devices are available for situations in which a hose may be left dangling from a faucet—such as outdoor garden spigots, a faucet in laundry washrooms, or situations where the faucet or hose is below the flood level rim of the fixture.
