The combination of an angle valve and anti-siphon device in one unit. The anti-siphon device is located downstream of the angle valve. Anti-siphon valves allow water to only flow in one direction. For irrigation purposes, it prevents water from the system from being siphoned back into the water supply line. Essentially, it stops unsafe water from entering a clean water supply such as the water that comes from your faucets or shower heads.
EXAMPLE:
In the picture below, there are four anti-siphon valves.
