How To Blow Out Sprinklers And Why It Matters For Winter Weather

If you installed an in-ground sprinkler system for your lawn, you know that it saves quite a bit of time versus manually lugging a hose and sprinkler around the yard. However, it also requires quite a bit more maintenance than the basic hose-and-sprinkler layout. One of the key maintenance tasks you should do before freezing temperatures arrive in late fall or early winter is blow all the water out of the system. You don't want to risk having leftover liquid inside your automatic sprinkler network when temperatures dip below 32 degrees Fahrenheit regularly or you could damage the pipes and other parts of the arrangement. When water freezes and becomes ice, its volume expands. The pressure of the expanding ice could crack the pipes, which are usually made of polyethylene plastic or PVC (polyvinyl chloride).

Because you should expect to spend at least $2,500 on installing a lawn sprinkler system, you'll want to protect your investment by maintaining it properly. Leftover water that freezes and breaks the pipes will force you to pay the cost of repairs, which could run you over $1,000. To fix the problem, you'll have to dig several inches into the ground to expose the pipes and track down the damaged section. You must then cut out the broken section and replace it, sealing both ends again. To avoid the hassle and expense of a repair, learn more about the two primary options for removing water from the system before winter arrives.

You can use air pressure to remove the water from the lines and sprinkler heads. Start by turning off the water supply to the sprinkler system. The shut-off valve should be on the home's side of the backflow preventer. It's common for the valve to be in a box just under the ground or inside a garage or basement.

You may have a small faucet near the valve. Open the faucet and use a bucket to catch water that comes from the main sprinkler line. This process won't remove all of the water, but some of the excess water will drain away. Turn off the timer for the automatic sprinkler system or set it to rain mode so it doesn't run all winter. If you turn it to the rain mode, rather than cutting off the power, the timer should retain all your operational settings for the following year.

You'll need an air compressor to finish the process of blowing water out of the system. Attach its hose to the sprinkler zone control valve. Use an air pressure setting of 40 to 80 pounds per square inch (PSI). Too much pressure could crack the pipes. Close the backflow valve to prevent air from escaping in the opposite direction from the sprinklers. Open the sprinkler zone farthest from the main line and start running the air pressure through the line. Move to different zones until you've blown out the water through the entire system.

Some underground automatic lawn sprinkler systems require you to drain the pipes manually, rather than blowing the water out. To start this process, shut off the main water supply to the sprinkler system. Turn off the timer for the system or set it to rain mode. You should have manual release valves located at the ends of the pipes and in any low points. Open one valve and let the water drain. Then shut it and move to the next valve. Continue the process until you've drained water through all the valves. Return to the main water supply valve near the backflow preventer (if your system has one). You may have a faucet next to the valve. Place a bucket under the faucet and open it. This should allow any remaining water in the line to drain away. 

If these methods of draining the lawn sprinkler lines seem like more than you feel comfortable doing on your own, you can try to hire a local sprinkler repair company, lawn care company, or plumber to drain or blow out the lines for you. You could expect to pay anywhere from about $40 to $200 for this work. 

As a final winter prep step, you may want to wrap the shut-off valve and faucet in insulation to try to prevent them from freezing. Things like foam pipe sleeves, insulation tape, and tarps all can protect any parts of the lawn sprinkler system that are above the ground.