Winterizing Your Backflow


A PVB is the most commonly used backflow device in the city of Houston.

Houston, Texas is not known for its cold weather but anything more than a few hours below freezing can wreak havoc on your irrigation system because the pipes are not buried very deep and the backflow device, if you have a Pressure Vacuum Breaker (PVB), is above the ground.  Understanding how to winterize your backflow device is something that everything home owner should know so as to avoid costly repair bills or the possibility of contaminating your water supply.

The backflow is the most important component of your irrigation system because it protects your family’s tap water from harmful contaminants that are present on the lawn; things like fertilizers, fungicides, pesticides and animal droppings.  These contaminants can be pulled into the irrigation system through capillary  action as the sprinkler heads finish spraying.  The backflow device acts as a stop-gap between the water that is contaminated inside the sprinkler pipes and your drinking water so it is very important that the backflow device is installed up to code and that it is functioning properly at all times.

An isolation valve is in a valve box usually near the meter or at the foot of the backflow as pictured on the left and will be a simple manual valve, usually a ball valve like the one seen in the image on the right which is in the open position.

There is a great deal of misinformation out there as to how to properly winterize your backflow.  The most common misconception (That you should simply turn the backflow handles off during the winter) significantly increases the chances that the backflow will break during a freeze and can lead to hundreds of dollars in repairs and inspections.  Winterizing your PVB properly can save you a great deal of money, is very easy and only takes one or two minutes.

The following procedure is the proper way to winterize your backflow (pvb) in the Houston, Texas area.  This is an important distinction because codes and installation methods differ greatly from state to state and city to city.  In the northern U.S., for example, your tap is probably in the basement and you most likely have a drain valve and a place to blow your system out with an air compressor.  These components were installed specifically for winterizing your sprinkler system.  Many far northern parts of the country will simply remove the backflow device for the entire winter season.  In the most southern parts of the country though, systems are not installed in the same manner because of the lighter winters and many of our plants will require some water during the winter months.

Step One is turning off the isolation valve. A ball valve is on when the handle is in line with the flow of the pipe and off when it cuts across the pipe. To turn it off give it a quarter of a turn so that the handle cuts across the direction of the pipe as seen on the right.

Important.  To properly winterize your Houston-area backflow you MUST have an isolation valve (cut-off valve).  An isolation valve is most commonly a simple ball valve that will be located in a valve box near your meter or at the foot of your backflow (often under the dirt, mulch or grass).  Isolation valves are standard components of an irrigation system and are currently state code though many older systems (and a great many systems that were not installed by a licensed contractor) may not have one.  If your system does NOT have an isolation valve then leave the backflow on and simply wrap it with insulation (towels or blankets; they even make an insulated weatherproof pouch for backflow devices that many of your local vendors may carry) during a freeze.  DO NOT turn the backflow off as this will significantly increase the chances of freeze damage and will usually result in a crack on the inside of the PVB.  We repair many PVBs every year that were damaged from home owners, landscapers and even misinformed irrigators turning the backflow off in this manner.  Once again; if you do not have an isolation valve then leave the backflow device alone and simply wrap it up during the freeze.  DO NOT turn it off.  You can give us a call (or your local irrigation professional) and have an isolation valve installed so that the backflow can be properly winterized in the future.

The test-cocks have a screw in the center of them that keeps the bleeder closed.  Those screws are closed in the left picture and open in the picture on the right.

The test-cocks have a screw in the center of each that keeps the bleeder closed. Those screws are closed in the left picture and open in the picture on the right.  Step Two: Open with a quarter of a turn to drain the water from the pvb.

Step One (Turn Off the Isolation Valve).  After locating your isolation valve step one is simply turning it off.  Not all systems will have a ball valve as pictured, some will have a gate valve (like the one on your hose bib) but a ball valve is the most common.  A ball valve will only turn a quarter of a turn in either direction and is open (or on) when the handle is in line with the flow of the pipe and it is closed (or off) when the handle cuts across the flow of the pipe.  If you have a gate valve (the kind of valve that turns your garden hose on and off) then just turn the valve clockwise until it is hand tight.

Step Two (Open the Bleeders) The next step will require a small flat head screw driver.  With screw driver in hand, standing in front of your pvb backlfow we are going to focus on the test-cocks.  The test-cocks are a pair of small nozzles that are used to test or drain the main cavity of the backflow.  Each of these test-cocks will have a small screw in the center (see picture).  Those screws, as with the ball valve, are open when the slot of the screw is in line with the flow of the water and closed when the slot cuts across it.  Use your screw driver to turn each of the test-cocks one quarter of a turn so that they are open (the slots should be horizontal).  This will allow the water inside of the backflow to drain from the unit.  DO NOT turn the screws more than a quarter of a turn or remove the screws from the test-cocks.  The water may have quite a bit of pressure when the bleeders are first opened, that is okay, it should subside rather quickly.

Step Three: First turn one ball valve to a forty-five degree angle and then turn the second ball valve to a forty-five degree angle so that your backflow looks like the one in the image on the lower right corner.

Step Three (Handles at Forty-Five Degrees).  Once the draining water begins  to slow we can finish the winterization process.  Leaving the test-cocks open to drain we are simply going to turn each of the ball valve handles on the backflow device to a forty-five degree angle (meaning that the ball valve itself is half open/half closed inside of the unit).  There will be one ball valve at the bottom of the backflow and one ball on the side of the backflow.  It does not matter which ball valve handle you turn first.

Success!!  You have now properly winterized your backflow.  If you do not plan on watering your landscape during the winter then you can leave your backflow winterized until the temperatures start to climb.  If you do water during the winter then you will perform this winterization process before each freeze.  It is always best to consult your personal landscaper or horticulturist to find out what the winter water requirements of your landscape are before making this decision.

Turning Your Backflow Back On.  To make your sprinkler system functional again you simply need to: 1) Open the isolation valve (this is going to shoot water out of the test-cocks but that is okay, we want to let any air or debris in the line escape.  2) Close the test-cocks with a screw driver (screw slots vertical) which will stop the water from spraying out of the backflow.  3) Return both ball valves to the full open position (handles in line with the flow of the pipe).  Your PVB will once again look like the one in the image featured at the very top of this article.

As always, TIS is here to help so if you need any advice or help winterizing your system then please don’t hesitate to contact us at:

John A. Taylor is President and CEO of TIS Services in Houston, Texas. He was awarded the 2013 EPA Partner of the Year Award for his water conservation efforts and he lectures on water conservation through innovative and conscientious irrigation across the country. TIS focuses on sustainable landscape and irrigation solutions. John is a veteran of the Unites States Marine Corps and lives with his wife and children in the Houston area.

John has blogged 12 posts here.

22 comments for “Winterizing Your Backflow

  1. Susan
    June 10, 2014 at 10:30 am

    What a great bit of information. Thanks.


  2. Raymond J.
    January 21, 2012 at 2:08 am

    Very easy, good info, great site. I’ll bookmark it.

  3. Kasten
    January 20, 2012 at 11:35 am

    We really appreciate your efforts John.

  4. Andrew Hawkins
    January 19, 2012 at 10:33 pm

    Is just turning my controller off not enough?

    • January 21, 2012 at 9:06 am


      Thanks for stopping by. Turning your controller off will help the landscape but this does not prevent freeze damage to the actual backflow device because there is still water in the pipes that rise up out of the ground and there is also pressure still being put against the backflow from the water meter. Turning the controller off when we drop below freezing for a few hours overnight is usually fine. Any substantial drop below freezing and you will want to winterize. Please let me know if you have anymore questions or need any help at all. Advice is always free.

  5. Nicole Portegosa
    January 19, 2012 at 7:58 am

    These guys are the bst, my system is working great.

  6. Lucas Oliver
    January 17, 2012 at 6:03 pm


  7. Isaac Maez
    January 12, 2012 at 6:02 am

    I won’t pay for my landscape guys to do this anymore. They were charging me $150. Thanx for sharing this much needed info.

  8. John
    January 5, 2012 at 11:32 am

    Is there a need to blow the lines out with an air compressor?

    • January 21, 2012 at 9:15 am


      No, not if you are in the Houston area. If you live up north then winterizing is a very different process. Most backflow devices up north are removed during the winter and the lines are blown out with a compressor as you mentioned. Our frost line here is between three and four inches deep so that step is not really necessary… not to mention that the beds here usually contain material that will need to be watered during the winter.

  9. Ericka Bechard
    January 1, 2012 at 9:06 pm


  10. Rich E.
    December 28, 2011 at 9:04 am

    Happy Holidays, TIS and families.

  11. Beth M.
    December 26, 2011 at 4:26 pm

    This is the kind of thing that makes your company so much different than the others, I couldn’t be happier, Mr. Taylor.

    • Sone
      March 14, 2014 at 11:17 am

      Hi. My water pressure is in area of 40 psi (on a good day) and I have a 1/2 main water line. Is there any way I can irnecase pressure and volume by possibly installing some kind of suction or booster pump? Thank you.

      • June 11, 2014 at 9:46 pm


        I am assuming that your 1/2″ main line is a copper line that goes to your house rather than the main line on your irrigation system? An irrigation main line should never be a half inch under any circumstance and would certainly create horrible water pressure by having an inordinate amount of friction loss. A half inch copper line for the house is pretty common. 40 psi, while below average is a far cry from bad. The City of Houston only considers psi under 30 to be a problem. I would not recommend an external pump for the house but a pump can definitely help with the irrigation. Send an email if you want more info.

        John A. Taylor

  12. Maria Adrian
    December 21, 2011 at 2:28 am

    Thanks a bunch. Very helpful.

  13. Paul
    December 20, 2011 at 1:41 pm

    Is this the article that the ABA is picking up for their magazine, John? Thank you for stopping by and checking on us, you guys are the best!! Merry Christmas.

  14. W. Willis
    December 17, 2011 at 2:45 pm

    Very well done and timely. Thanks lot Taylor Irrigation.

  15. Ben
    December 17, 2011 at 5:08 am

    I just did nmine and it was as easy as you said it would be. Great resource!

  16. Paul Everett
    December 15, 2011 at 5:59 am

    THis will really help my entire staff John as you know we have dozens of back flow preventers on site. Really invaluable information and very much appreciated. Merry Christmas.

  17. Casandra Maria
    December 13, 2011 at 1:58 pm

    It was so easy I did it while my husband was at work! Kudos

  18. Paul Green
    December 12, 2011 at 5:18 pm

    Great info and couldn’t be timed any better. Happy Holidays and cheers, John.

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