How to Drain a Sprinkler System For The Winter

How to Drain a Sprinkler System for Winter

It is particularly important for you to understand how to properly and completely drain a sprinkler system for the winter when you live in an area that gets below freezing temperatures during the colder winter months.  A properly drained sprinkler system will allow the water lines and pipes to remain unfrozen, eliminating the chances for cracks or breaks in the pipes. 

Draining a sprinkler system in the fall before the cold sets in for the year shouldn’t take very long and by following these simple steps you can guarantee you will get the longest life out of your irrigation system.

The Basics of Draining a Sprinkler System for the Winter

  • Find the main water valve to the irrigation system and turn it off.
  • Adjust all ball valves and backflow test cocks to a 45 degree angle.
  • Open each of the valves in the pipes to release the water pressure.
  • Allow all of the water to drain from the sprinkler heads.
  • Turn your controller off.

While this all sounds simple and is a straightforward process it can be a little confusing the first time you do it.  Check out the complete steps to draining a sprinkler system for the winter below for both automatic irrigation systems and manual irrigation system.

Step by Step Guide How to Drain a Sprinkler System for the Winter

The steps are similar whether you are draining an automatic irrigation system or a manual irrigation system.  Many homeowners will hire a professional for the first Winter’s winterization to watch and learn and then do it each year going forward on their own.  Every system has its own unique winterization process depending on the layout of the zones and the equipment that you are using.

Automatic Irrigation Systems

  1. Shut off the mainline valve by closing it.
  2. Keep an irrigation zone that is the furthest down your system open so that the water pressure on the mainline is relieved. It is important that while running the air compressor element to drain the line that the zone valve is kept open.
  3. Using the quick hose coupler valve attach the hose from your air compressor to the irrigation system.
  4. Set the pressure on your air compressor to 50 pounds per square inch. Some compressors you will need to watch the PSI gauge and turn off the compressor when it reaches the 50 PSI mark.
  5. Allow the air in the compressor to be sent into the system. You should see all the sprinkler heads pop up and begin to emit the residual water in the system in that furthest zone.
  6. After a couple of minutes have past switch the controller to the next zone, keep the controller on and systematically go from zone to zone until they have all been blown out with air removing the water.
  7. Go through the cycle again and sometimes you may even need to do this multiple times until only a fine mist of water gets emitted from the sprinkler heads.
  8. Turn off the compressor after most of the water has been expelled from the system.
  9. Disconnect the compressor from the irrigation system with the hose quick valve coupler.
  10. Turn off the controller for your irrigation system.
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Manual Irrigation Systems

Draining the irrigation lines for a manual irrigation system is like an automatic system, however you will need to manually adjust the zone valves.

  1. Shut off the mainline by closing the valve.
  2. Select the irrigation zone control furthest from the air compressor value and open the manual shutoff handle to relieve the water pressure that is present in the mainline. Always make sure at least one zone is open while running your air compressor while connected to the system.
  3. Set up the air compressor and attach the hose to the quick hose valve coupler.
  4. Set the pressure on your air compressor to 50 pounds per square inch. Some compressors you will need to watch the PSI gauge and turn off the compressor when it reaches the 50 PSI mark.
  5. Allow the air in the compressor to be sent into the system. You should see all the sprinkler heads pop up and begin to emit the residual water in the system in that furthest zone.
  6. After a couple of minutes have past switch the controller to the next zone, keep the controller on and systematically go from zone to zone until they have all been blown out with air removing the water.
  7. Go through the cycle again and sometimes you may even need to do this multiple times until only a fine mist of water gets emitted from the sprinkler heads.
  8. It is important on a manual system that the pressure in the lines are allowed can dissipate before closing the valves.
  9. Disconnect the compressor from the irrigation system with the hose quick valve coupler.
  10. Close any valves that were still open for zone controls.

Draining Manual Irrigation without Air Compressor

There are systems that can be designed to allow a pure manual drain by just opening the valves and allowing the water to just flow.  These require precise placement as if you do not place the drain out at the lowest points you will leave residual water which may cause a problem to your system.

It is recommended for these systems to leave the valves open until you are ready to close them the following spring and start irrigating again.  By leaving them open it allows for a little expansion to occur if the weather drops below freezing.  These are a great option for individuals that live in warmer climates and rarely experience freezing temperatures.

Blowing the system out with an air compressor is the only way to guarantee that you have removed all the water from the system and highly recommend for locations that experience periods of time below freezing.

Which Type of Irrigation System is Easier to Winterize?

If you are trying to learn about draining an irrigation system for the winter before making a buy decision, I highly recommend considering investing in a real controller and an irrigation system that allows for air compressor to blow out the lines before closing them for the cold months.  Blowing the lines out with air is the most effective way to winterize your sprinkler system.

Draining manual irrigation lines without an air compressor is only as good as the installation.  If a line ends up having a couple of high spots it is possible to retain enough water in the line to freeze, expand, and rupture the line.

Even if you are not ready to spring for an automatic controller for your sprinkler system, I highly recommend setting it up a blow out system.  Air compressors are cheap and if you don’t have one already you will immediately find a ton of additional uses for it aside from your annual sprinkler system winterization.

How Do You Know You Drained the Sprinkler System Properly?

When you turn the valve for the first zone that you are draining you will notice that it comes on strong at first and then begins to start to wane, the water pressure is dropping and getting the majority of the water out.  Make sure to follow a simple pattern as you go from zone to zone so that you ensure that you do not skip a zone.  There is nothing wrong with double checking each zone one last time before turning off the air compressor to make sure you have not made any mistakes in your winterization plan.

If using a manual drain system, you can walk away after opening all the valves.  Come back to check later one more time and make sure that you didn’t miss a single valve for the system otherwise you will likely be dealing with a irrigation line repair or worse in the spring.

For an air compressor system once you get to the series of steps for draining each zone you will get to a point where the fine mist from the pop up sprinkler heads fade to a fog that is what you are looking for to move to the next zone and complete the job.  The minimal amount of water left will not cause any problems to your system.

A Few Extra Things to Remember When Draining a Sprinkler System

  • Turn off the main water line before working.
  • Follow a step by step by plan outlining each valve you need to turn and when.
  • Double check your work to verify the lines have been completely drained before winter.

Learning how to drain a sprinkler system for the winter is an excellent skill for any home owner living in colder climates.  You do not need to learn how to winterize all types of sprinkler systems, but you want to know how to precisely operate yours to provide this essential maintenance.  If you are new to draining a sprinkler system talk to an irrigation pro to come out and show you how your system works or see if a friend or neighbor can help walk you through it for the first time so that it is done right and you do not end up with a lawn destroyed by a flooded irrigation line come spring time when you turn it on to start watering again.