The web's mother lode of free irrigation information!

Irrigation Product Listings & Reviews

Irritrol 311A Anti-Siphon Valve


The 311A Anti-siphon valve is Irritrol's top-of-the-line anti-siphon valve. At one time this valve was sold under the Hydro-Rain brand name.

Model Numbers:


Manufacturer's Performance Data:

311A Series Valves - Pressure Loss through Valve
Model Size 1 GPM 5 GPM 10 GPM 15 GPM 20 GPM 30 GPM
311A-.75 3/4" 5.5 PSI 6.0 PSI 8.0 PSI 9.0 PSI 11.0 PSI Do not exceed 20 GPM
with 3/4" size
311A-1 1" 5.5 PSI 6.0 PSI 7.5 PSI 8.5 PSI 10.0 PSI 18.5 PSI


This is a good quality anti-siphon valve, although it is a bit ugly! While Irritrol considers this valve suitable for commercial systems, it should be noted that commercial systems rarely use anti-siphon valves. The nylon upper body is very high quality, but the benefits of the nylon are almost completely defeated by combining it with a PVC lower body. So it has the same pressure rating as the less expensive PVC models. The 311A is actually a hybrid of two separate items. Essentially it is a manual anti-siphon valve body with an electric actuator conversion kit installed on it. An internal bleed means it doesn't spit water when operated manually. A captive plunger makes it easier to work on. This valve can be repaired without removing it from the piping. The optional OmniReg® device allows the valve to control the downstream pressure at a more or less constant level (see separate listing for the OmniReg®).

The 311A anti-siphon valve has very high friction loss compared to Irritrol's other anti-siphon valves. I really don't see the point of spending more money for this valve unless you need the optional OmniReg® modular pressure regulator. If you have water pressure high enough to need the pressure regulator, you probably want a valve rated higher than the 150 PSI maximum for this valve. The rule of thumb is that the pressure rating of a valve should be at least double the actual static water pressure. Take a look at the installation rules for the Irritrol 2700 series anti-siphon valve: Click here. The same important installation rules apply to the 311A and all other brands of anti-siphon valves.