Carmen Boles

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How To Blow Out Your Sprinkler System

Here’s how to blow out and winterize your irrigation system!

Step 1: Shut off the Main Water Supply and Drain

Before you proceed, you will need to turn off the main water supply. This ensures that no additional water flows into the piping. See picture below.

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Once you turn off the water, you’ll also need to open the hose bib on the main water supply that’s connected to the irrigation system to let the remaining water drain out. See picture below for example.

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Step 2: Switch off the Timer

set timer on sprinklers connected with valves

If your watering system uses a timer, you will need to shut it down. This reduces the risk of electrical or mechanical faults while the irrigation system is offline.

Depending on the type of timer you use, you can also set it to rain mode. That way, your programming will remain unchanged, and you can simply set it back to how it was  after the winter. 

Step 3: Attach the Compressor 

Now you’ll need to attach an air compressor that provides a volume of at least 30-50 cubic feet per minute to the irrigation system. You will need a flexible hose to connect the compressor (using a coupler). 

Close the airflow valves on the compressor and attach the coupler to the end of the air compressor hose, in turn attaching it to the air compressor blow out adapter on the irrigation system.

compressor  30 to 50 cfm to winterize sprinklers attach after backflow valves
Image courtesy

Step 4: Blow Out the Sprinklers 

Ensure that you blow out the zone farthest from the mainline first. This will ensure that you can adequately complete a zone-by-zone blow out. 

If your system is on uneven terrain, start your sprinkler blow out with the higher level zones first. The higher zones may need higher pressure, so you need to get them out of the way before lowering the pressure on the compressor.

Close the backflow valves on the irrigation system, then turn on your compressor, keeping your eye on the pressure.

Note: turn the compressor on very slowly and gradually increase the pressure until you reach the recommended PSI requirement for your sprinkler system.

Once the lines start filling up with air, you will see the water coming out of all the water taps attached to the sprinkler line. When all the water sprays out of the open taps, close all of the taps except the one that’s attached to the air compressor.

Remember these important sprinkler blow out safety tips:

  • The extremely high pressure of compressed air can be dangerous, so ensure you wear safety glasses. 
  • Don’t look directly over the sprinkler heads to avoid taking a hit from the pressurized air or debris.

Now starting with the irrigation head farthest from the compressor, turn on each sprinkler head. Do this for all the sprinkler heads as you work your way towards the main water line. Shut off each head when it stops spraying water.

Alternatively, you can turn on each zone manually or on the controller. Wait for the water spray to stop, then turn off that zone and proceed to the next.

Take care not to blow out each head or zone for longer than you need to. Once the water spray stops, you need to close immediately.

Once you’re done blowing out sprinkler-by-sprinkler or zone-by-zone, close the shut-off valve on the compressor.

Then alternately open and close the backflow device valves a couple of times to release any pent-up air pressure. 

Remember to insulate all the above-ground fixtures of your irrigation system to prevent them from freezing.

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