Anti-Siphon Valves

Anti-siphon valves must be installed above ground, at least 6 inches higher than the highest sprinkler head or emitter in the irrigation zone. Since they function both as control valves and backflow preventers you’ll usually want to install them at the start of each irrigation zone.

No, anti-siphon valves are designed to be installed above ground, typically at least 6 inches higher than the highest sprinkler head on the zone. This elevation is what allows the built-in atmospheric vacuum breaker to prevent contaminated water from siphoning back into your main water supply. If you need a below-ground backflow preventer, consider using an in-line valve paired with a separate backflow preventer rated for underground installation.

A properly functioning anti-siphon valve should not spray water continuously while the sprinklers are running. This is often caused by debris stuck in the air vent, a worn diaphragm, or high water pressure forcing the valve to vent. It can also happen if the valve is installed below the highest sprinkler head. Cleaning the valve, replacing the diaphragm kit, and checking the installation height usually fixes the issue.

You need one anti-siphon valve for each irrigation zone. While most residential setups will only require a single valve, this also means that larger commercial setups will need an anti-siphon check valve for each section of a garden or lawn. Each valve acts as a control valve and a backflow preventer for its specific zone.