Moreover, if the water freezes in backflow assembly, it can damage and can even crack the brass body of the internal components. You can use one of the following methods, as applicable, to winterize your sprinkle system and outside hose bibs.

Manual Method

If in your sprinkle system, there are manual drain valves attached at the end-points of the irrigation piping, you should use the manual drain method to winterize the system. You can follow the following steps.

1. Turn off the irrigation water supply in the basement.

2. Open all the manual drain valves to drain the water from the mainline.

3. After you have drained out the water, now you have to drain all the water that might be remaining between the irrigation water shut off valve and the backflow device. Generally, there remain some water in the backflow, the piping and the sprinklers. However, it depends on where are the drain valves located.

4. In order to drain that water, open the boiler drain valve, or the drain caps on the stop and waste valves whichever is applicable for your system.

5. Open the test cocks located on the backflow device.

6. In case, you have check valves in your sprinkle system, pull up on the sprinkle and drain the water out from the bottom of the system body.

7. Once you have drained out all the water, close all the valves.

Automatic Method

If in your sprinkle system, there are automatic drain valves attached at the end-points of the irrigation piping, you should use the Automatic drain method to winterize the system. You can follow the following steps.

1. When the pressure in the piping is less than 10 PSI, the automatic drain valves of the sprinkle system automatically open to drain water. You just need to activate this automatic feature.

2. Turn off the irrigation water supply in the basement.

3. In order to relieve the system pressure, activate a station. The water will automatically drain out of the machine.

4. After the water has drained out, now you have to drain all the water that might be remaining between the irrigation water shut off valve and the backflow device. Generally, there remain some water in the backflow, the piping and the sprinklers. However, it depends on where are the drain valves located.

5. In order to drain that remaining water, open the boiler drain valve or the drain cap on the stop and waste valve whichever is applicable for your system.

6. Open the test cocks located on the backflow device.

7. In case, you have check valves in your sprinkle system, pull up on the sprinkle and drain the water out from the bottom of the system body.

Blow out Method

In order to use this method, you need an air compressor with a Cubic Foot per Minute (CFM) rating of 125-185 for any mainline of 2" or less and a PSI of 50-80.

You can rent this air compressor from your local equipment rental yard. Now, follow the following steps.

1. Attach the compressor to the mainline via a quick coupler, hose bib or other type connection. You can find these connections before the backflow device.

2. Open the test cocks located on the vacuum breaker.

3. Turn off the irrigation water supply located in the basement.

4. Open the drain on the supply line to drain the water.

5. After the water has been drained out, close the drain.

6. Now you have to connect the airline.

7. Attach the air compressor hose to the fitting while make sure the compressor valve is in the closed position.

8. Now locate such a station on the controller that is not only furthest from the compressor but also is the zone or sprinklers highest in elevation. Activate this station.

9. In order to allow air to slowly enter into the irrigation system, slowly open the valve on the compressor. Make sure, you have not yet closed the backflow isolation or Test Cock valves.

10. Be careful that the air pressure is constant at 50 PSI. However, you can increase the pressure allow the sprinkle heads to pop up and seal. Still, never exceed the air pressure 80 PSI.

11. Repeat this process for each station or zone to activate the same.

12. Once you are through, make sure there is no water on any of the heads.

Hence, here we see the various ways that you can use to winterize the sprinkle system and outside hose bibs. However, it is always recommended for you that if you want to use the blow out method, do not do it yourself until and unless you have a clear understanding of all the technicalities. Otherwise, it is better to hire a qualified licensed plumbing contractor to perform this method of winterization.