Getting Ready for Winter

Many parts of the USA blow out their systems with compressed air to winterize irrigation systems. But in states where there is freezing weather, but the soil freeze depth is less than 18 inches, we simply turn off the,water supply to the Irrigation system with the isolation valve. The next step is to close the brass ball valves on the pressure vacuum breaker or RPZ. Then take a flat head screwdriver and open the test cocks to drain water from the backflow device. Then turn the backflow ball valves to a half on/half off position. This protects the backflow from damaging internal parts and cracking of the lead free backflow decice.


I live in an area (Dallas) where turning off the sprinkler system is only required when it gets really cold - once or twice a season.

All these years all I’ve ever done is “turn off the water supply … with the isolation valve” (and for me this is simply a separate, 2nd water meter). I had no idea that I’m supposed to “… close the brass ball valves on the … vacuum breaker. …open the test cocks to drain water from the backflow device. …turn the backflow ball valves to one-half …”


Best regards,


Is your backflow in the ground? If it is a double check its not necessary. Here is a video that shows how to winterize a Pressure Vacuum Breaker


In new England and really cold places air compression is used to blow out the whole system.

Thank you.

Yes, my double check valve is in the ground, out in the ROW between the curb and the sidewalk, with a 3/4" water meter between it and the main water line.

Very helpful. Thanks!

Best regards,


Then no need to bother winterizing your double check because it is below the frost line. Backflow freeze damage is a common issue in Oklahoma City. Double checks are not allowed here because we follow the national standards that classify irrigation as high health hazard potential for cross-connection (backflow). Only above ground pressure vacuum breaker or reduced pressure principle device.

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Interesting. Thank you. Bill

It will protect the backflow, but if the irrigation pipe has standing water in it and it freezes, the pipe may crack. You can use pressurized air, or sometimes a shop vac to remove the standing water in the pipes.

Robert, I live in Edmond, OK and I’m not sure where my backflow valves are located, there is an above ground looking rock cover hiding something, possible thats where it is? I’ve lived in this house for 3 years now and have not ever done anything with my system. Its been good for the past 3 years, but am I just waiting for disaster?

Yes, your backflow is under the rock. If a deep freeze is in the forecast its a good idea to winterize your backflow. Do you have an isolation valve down by your water meter. Do you have a heat tape? Check it. I’m in Oklahoma, too. Just an extra measure of protection if we are to go into several days of below freezing temps.

If you are not going to use the drain plugs near the backflow valve to attach an air compressor to blow out the entire line, then where are you going to attach the compressor?

What is wrong with closing the ball valve proximal to the back glow preventer, and then using the second drain plug below the backflow device to introduce the compressed air, provided you do not exceed 60 psi?

I really do not know any other method. But in the Certified Irrigation Technician class from the Irrigation Association they state pressure should never exceed 30 psi. Perhaps someone from the Midwest or New England can answer.
There are standard procedures that all follow. Do not deviate from standard methods.

Fine, then blow out the lines with 20 psi air pressure. You won’t need more than that.