How to protect an underground sprinkler system from freeze?

Given where we live, I have to "winterize" ours ever year. The first thing I do is turn the water off to the system. Second I remove the back-flow preventer and place it in the garage or basement. There are some sensitive gaskets in there that can deform and cause it to leak when you turn the water off. Lastly, you want to make sure that all the water is out of the system. We have a fair amount of elevation in ours, so all I have to do there is cycle the valves a few times and the entire system drains. I simply turn on the timer to open the valves for a few days after I've turned the water off.

If you don't have a good low point in the system, you can take an air compressor, open the sprinkler valves and blow air through the system until all or most of the water is out of the pipes. Make sure all the valves are open as you can cause problems if you put too much pressure on the system.

That's about it. Even with all of that, I still have to replace a few heads and sometimes repair lengths of pipe almost every year.

Turn the water off to the system then you can connect your air compressor to the back flow preventer and blow all the water out of the system.

You don't have to do all of that. Just shut the valves off on both side of the backflow preventer and drain the water out of it with the little release valves on the side. There are usually 2 small valves on the side of the preventer. That is the only thing that will freeze. If you want to take it a step further, just make sure you have the exposed lines in the preventer loop insulated.

Pour antifreeze in the pipes

Maybe disconnect it and blow the water out with an air compressor?

Ok, should have read all the replies before I bothered.

quote:

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Second I remove the back-flow preventer and place it in the garage or basement.

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Never heard of that doing that before. Why not just empty the water with an air line instead and leave the BFP intact?

Post a pic of your backflow preventer

Just run your sprinkler all night and through the freeze.

Keep in mind the guy that responded shows that he is from Utah. If so, his approach has to be more severe than us in the southern states (and I'm north of Atlanta).