How to Winterize Sprinkler Systems

In colder climates the ground can freeze three or more feet deep. Because sprinkler systems are within that zone, they are at risk of freezing. When left over water in the sprinkler systems freezes the water expands and can cause the pipe to burst. If you have above ground piping like an RP or PVB backflow, that equipment can also be damaged by freezing temperatures. When temperatures start to creep toward 30 degrees, it is time to winterize your sprinkler system—don’t wait any longer. Repairs to damaged pipes, and especially backflows, can be expensive.
Winterize Sprinkler Systems

There are two main ways to winterize your sprinkler system:

Install Automatic Drain Valves

Automatic drain valves are attached to the sprinkler system, so that when the water is turned off, and pressure hits the drain valve, it opens and drains any remaining water in the sprinkler line. The drain valve has a filter cover to prevent any debris from clogging the valve, and the drain itself is a rubber diaphragm. Some automatic drain valves also include backflow preventers to prevent any built-up ground water from entering the sprinkler system. The drain valves are connected to the sprinkler line using a PVC T pipe and are installed at the low spots of the sprinkler line facing down so water can drain into the ground. Each zone should have two to three drain valves to ensure the system is thoroughly drained. Automatic drain valves work in most soils and are a decent alternative to blowing out the system before each winter. Also, if you live in a climate with unpredictable quick freezes, automatic drain valves may be a system saving choice.

How to install automatic drain valves

  • Turn the sprinkler system off using the valve for each zone.
  • Decide where you want to place your drain valves (low points in the line) for each zone, and how many automatic drain valves to install.  Dig up those areas to help you determine the size of the PVC pipe used.
  • Gather your materials:
    • Automatic drain valves
    • PVC T pipe for each valve (make sure the drain valve and T pipe are the same thread size), and that you get the right size T pipe to fit the line.
    • Plumbers tape
    • Measuring tape
    • Saw to cut through sprinkler line (PVC pipe)
    • 80 grit sandpaper
    • PVC primer and PVC cement
    • Face mask as indicated in primer and cement instructions
    • Specialty fittings (telescope coupling, compression coupling) if needed
    • Shovel
    • Work gloves
  • To start, attach the automatic drain valves to the PVC T pipe. Consider using plumbers’ tape on the threads to help seal the connection.
  • Next, using the measuring tape and saw, cut a small portion of the sprinkler line to make way for the PVC T Pipe. Remember, you can always cut more if needed . . . be conservative. If you don’t have a lot of room, or over cut, you may find you need to use additional specialty fittings.
  • Using the sandpaper, de-burr (remove plastic burrs from sawing) the cut edge of the sprinkler line. This will help to ensure a good fit.
  • Prepare the sprinkler line and PVC T Pipe for coupling by wiping the inside of the T Pipe and the outside of the sprinkler line with PVC primer. Make sure to follow all safety and product instructions (masks, gloves, dry time).
  • Next spread an even layer of PVC cement on the inside of the PVC T Pipe, and the outside of the sprinkler line where you will connect them. Working quickly connect the pipes a quarter turn from their final orientation. Once connected, twist the pipes into the final position and hold the pipes together for 15 – 20 seconds. Again, make sure to follow all safety and product instructions while using these aggressive chemicals. Also, make sure to match the solvent used to the pipe material. If your sprinkler systems isn’t PVC, you need to take that into consideration.
  • Once the automatic drain valves and PVC T Pipe fittings are all in place turn the zone valves back on and let the sprinklers run. Then turn the sprinkler system off and check to make sure each valve is draining its line correctly.
  • Before burying the sprinkler system, quickly map out where you put each automatic drain line for future reference.

Automatic drain valves do the hard work of getting water out of the line. However, in order to fully winterize your sprinkler system, you will also need to make sure that you winterize your RP or PV backflow, and vacuum breaker—basically any sprinkler system parts located above ground. You can do this by stopping the water supply, opening valves, and insulating the parts. Also, don’t forget to shut off the water supply and drain the supply line to the sprinkler system. Lastly, shut off the sprinkler system entirely for the winter –especially if you have it on a timer!

Drain and blow out your sprinkler system

Not everyone is a fan of automatic drain valves. Automatic drain valves do waste water because they automatically drain the water from the sprinkler pipes each time the sprinkler shuts off. Normally that water would be used by the sprinkler or sit in the pipe until. This wasted water will lead to a higher water bill. Additionally, automatic drain valves can fail, though unusual, and lead to a broken pipe.

Instead of automatic drain valves, many choose to “blow out” their system. This involves blowing pressurized air through the sprinkler system to remove any remaining water.

How to blow out your sprinkler system:

  • First shut the water off to the sprinkler system.
  • If you have a backflow, turn the valve located after the backflow to the closed position. This is to prevent compressed air from going back into the backflow.
  • Next, locate the point of connection for the air compressor hose and slowly remove the blow out cap in case pressure has built up.
  • Using an adapter, connect your air compressor to the pipe.
  • Next, if you have more than one zone, you will be manually turning on your sprinkler system zone by zone. Do NOT turn on the compressor before turning on a zone. If the sprinkler isn’t open the compressed air can damage the sprinkler system. Turn on zone 1.
  • Turn on the air compressor and keep it running until the water coming from the sprinkler system changes from a steady stream to a fog. Do this for each zone and then turn off the air compressor. Remove the compressor and the adaptor and return the blow out cap without fully connecting it.

Note: your air compressor should not be more than 80 psi. Also, normal air compressors will work, but they do not have the volume of air needed to blow out the system quickly and thoroughly. It will take a significant amount of time to blow out the system using a homeowner’s standard air compressor. You may want to rent a compressor that delivers more volume . . . but don’t go over 80 psi.

  • Once you are done blowing out the sprinkler line you need to return to the backflow to remove the water that is still in the system from the home’s water supply to the backflow. Once at the backflow turn the ball valves and test cocks a quarter turn to allow water to escape if trapped.
  • Lastly, you can drain any remaining water from the system at the point of connection inside the house.

Installing automatic drain valves, blowing out your system, and even weatherizing parts of the sprinkler system above ground, can be complicated tasks. It might be worth it to have a professional come and show you how to do it at least once. Paying to have your system weatherized will, in most cases, be less expensive than the repairs and mess that come with damaged pipes or equipment. If you need help winterizing your sprinkler system, or any of the plumbing in your house, don’t wait! Give us a call today and we will come on out and get you ready before the first freeze.

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