Properly winterized pipes will keep the water in your house from freezing and save you a lot of trouble later on. Sometimes, just setting the faucet to drip is enough, but others require an irrigation “blow out.” For this, there are a few methods:
Manual Drain Method
Follow this method if your manual valves are visible at the end and at lower points of your irrigation piping.
Once the valves are located, draining them is simple.
Shut off the water supply and make sure that all of the draining valves are open.
Then wait for the water to empty the mainline and move on to draining the stop and waste valve or boiler drain valve (they’re very similar but the one you have depends on your area).
Your sprinklers retain water even if they’re not on, so pull up each sprinkler head and let the water drain out of the bottom.
Be sure to check for remaining water in the backflow and piping. A Shop-Vac can get the rest of the water out.
Don’t forget to close all of the drain valves when you’re finished.
Automatic Drain Method
First, you need to shut off your water.
Then, move down the mainline and turn one of the systems or sprinkler heads to alleviate the system pressure. This will keep your pipes from freezing.
You also need to drain any excess water stuck between the shut-off valve and backflow device, so open the boiler drain or stop and waste valve on the backflow device.
Next, pull up the tops of each sprinkler head and let the water drain from underneath it, otherwise, it could be damaged in the freeze.
Check for any remaining water in the system and use a Shop-Vac to get it out.
Be sure to close all of the open valves when you’re done.
Here, it is incredibly important to make sure that you’re wearing ANSI-approved safety eye protection! This method involves compressed air, which can be extremely dangerous if there is any flying debris.
Even with eye protection, avoid standing right on top of the pipes, valves, and sprinklers, during the blowout.
Along with ANSI-approved safety eye protection, you’ll need an air compressor (larger than 3 HP) which can be cheaply rented from a local equipment store.
Once you have the proper equipment, attach the compressor to the mainline via a quick coupler (you could use a hose bib or anything you’re comfortable with). Do not connect through the backflow device, compressed air should never be used to clear a backflow device.
To start, turn off the water supply and turn on the sprinklers at the far end of your irrigation line, closing those at the start. This will allow you to blow all of the water along the line out at the very end.
Now, slowly open up the compressor to gradually allow air into the irrigation system. Do not exceed 80 PSI when blowing out an irrigation system.
Continue with the compressed air through each zone until you can no longer see water coming out of the sprinkler heads.
When all stations/zones are dry, stop blowing air through them. Overheating pipes can be just as damaging as freezing them.