DIY Irrigation Winterization

Crash course on common residential lawn irrigation system design

Generally your irrigation system connects to the water supply just after your water meter, goes into your irrigation system main shut off valve, proceeds into backflow preventer, proceeds into your irrigation master valve, and then branches into your station valves and then into your individual irrigation heads (sprinklers).

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Code requires that all pipes to be 6” underground, and due to our relatively mild winters in southern states, this means we usually don’t do a full blow-out, and are generally just trying to protect backflow preventer, valves, and sprinkler heads by relieving water pressure from those components.

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Steps to winterize irrigation system in Central Texas (and most southern states):

1. Locate your irrigation system main shutoff valve, which should be very close to your water meter, and between the water meter and backflow preventer. Close it (handle of valve parallel to pipe is open; move handle to be perpendicular to pipe).

2. Locate your backflow preventer, which should be just downstream of the irrigation main shutoff valve. If you have a septic system, it should be above ground and covered by thermal insulation material; otherwise it could be underground in an elongated in-ground box with a cover that you should be able to see or find with a long screwdriver. Open the thermal protection or in-ground box cover. If you find wasps in there, they should be very sluggish this time of year; if you find a snake, it is most likely a non-venomous garter snake; exercise proper caution in either case.

3. Although it is perhaps the most critical device of the irrigation system, to a non-professional, backflow preventer appears (at least backflow preventers mostly used in southern states) as an elongated metal device with a bunch of weird valves put together. Your system might have water pressure release valves on each side of the backflow preventer; if they are there, open them.

4. Go to your irrigation controller, and manually run all zones for 1 minute; this should relieve most pressure from the system.

5. Take a flat-head screwdriver and go back to your backflow preventer. You should be able to find 2 to 4 check valves, depending on the type of backflow preventer. Check valves are small valves (often under rubber covers) operated by a flat-head screwdriver (perpendicular to the pipe is closed, parallel is open). Move them all to half-open (45 degrees) in any order; you should see some water draining from the backflow preventer.

6. Go to your irrigation controller again, and manually run all zones for 1 minute again, but in reverse order (i.e. if you have 6 zones, run zone 6 first, then zone 5, etc.). This step is not critical, but it helps in cases when zone 1 is lower elevation than zone 6 - if this is the case, our step 4) (running all zones for 1 minute) didn’t push zone 6 water into zone 6 sprinkler heads but pushed it into zone 1. At this point, all your sprinkler heads and zone valves are winterized as best as possible without full blowout.

7. Go back to your backflow preventer. Set all check valves to 45 degrees (half-open) - according to some reports, this minimizes chances of expansion of water trapped behind your ball valve to cause damage to the check valves (we are still unconvinced by physics behind this recommendation, but better safe than sorry). Close your water pressure release valves on each side of the backflow preventer if you opened them in step 3. Put back your thermal cover or in-ground box cover.  At this point, your backflow preventer, and the whole irrigation system is winterized.

8. Get some faucet freeze protectors from HEB, Home Depot, or Lowe’s, and put it on your outside faucets (wrapping a heavy towel around faucet should be sufficient if faucet freeze protectors are already sold out). Some people also recommend adding insulation above each irrigation zone valve - so far we have not found this to be necessary.

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We are thrilled to help you with all your irrigation questions and needs, and it is better to get ready early with help of a licensed professional, but in a pinch you can do it yourself.

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Irrigation in Texas is regulated by the Texas Commission on Environmental Quality (TCEQ), MC-178, P.O. Box 13087, Austin, Texas 78711-3087. TCEQ's website is: www. tceq.state.tx.us.