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How to Properly Winterize Your Backflow Preventer
Turn off shut-off valve/drain 2 test screws/ turn 2 valve handles 45 degrees & drain additional drain valve on lower supply side leg if present.
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 backflow device, which must be a PVB or an RPZ within Houston city limits, is installed above ground. Understanding how to properly 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. This article walks you through winterizing a PVB device step by step and includes pictures to guide you. It is very easy, takes just a minute or two and all you will need is a small flat-head screwdriver.
Let’s start by learning about the purpose of the backflow device because it is the most important component of your irrigation system. The backflow device is NOT an irrigation “shut-off” though it does turn water off to the irrigation system when closed.
The sole purpose of a backflow device, which is required by state and local code, is to protect your family’s tap water from harmful contaminants present on the lawn. Things like; fertilizers, fungicides, pesticides and animal droppings are present on most all lawns as well as the surrounding areas. These contaminants can be pulled into the irrigation system through capillary action as the sprinkler heads finish spraying and return to their retracted positions below the ground. The backflow device prevents the contaminated water from mixing with the potable water you and your family use daily so it is very important the backflow device is installed up to code, is well maintained and functioning properly at all times.
There is a great deal of misinformation out there as to how to properly winterize your backflow. The most common misconception is that you should simply turn the backflow handles off and wrap the device up during the winter or when a hard freeze comes. This actually significantly increases the chances that the backflow will break during a freeze and can lead to many hundreds of dollars in repairs and inspections. Winterizing your backflow device properly can save you a great deal of grief and money, and it only takes one or two minutes.
The following procedure is the proper way to winterize your PVB backflow device 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.
Before You Start PVB Backflow Winterization
To properly winterize your Houston-area backflow you MUST have a shut-off valve. A shut-off valve is most commonly a simple pvc ball valve that will be located in a small, round, green valve box near your meter or at the foot of your backflow (often under the dirt, mulch or grass). Like in the above picture. We often see them mounted at the bottom of the inlet leg of the backflow device which is not ideal as it is subject to freezing.
Shut-off valves are standard components of an irrigation system and are currently state code though many older systems may not have one. If your system does NOT have a shut-off valve then leave the backflow on and simply wrap it with insulation, towels, blankets or they even make an insulated weatherproof pouch for backflow devices that many of your local vendors may carry. 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 metal PVB body just above the first ball valve on the intake side.
Once again; if you do not have a shut-off valve then leave the backflow device alone (do NOT turn it off) and simply wrap it up during the freeze. Give your local irrigation professional a call and have a shut-off valve installed so that your backflow can be properly winterized in the future.
3 Steps to Winterize Your Backflow Preventer
1. Turn Off the Shut-off Valve
After locating your shut-off 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 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 simply turn the valve handle clockwise until it is hand tight.
2. 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 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 metal fitting they are attached to and are closed when the slot cuts across it. Use your screw driver to turn both of the test-cocks one quarter of a turn so that they are open. Don’t be alarmed by water that may shoot out of the test cock with some pressure, it will quickly die down. This allows the water inside 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. When the water draining from the device subsides, give the device a few light shakes to get a little more water out of the device. You just created an empty cavity in the device so when the water left inside the PVC legs freezes and expands, it has a place to go so it will not fracture the the device or the pipes.
3. Handles at Forty-Five Degrees
Once the draining water begins to slow we can finish the winterization process. Leaving both 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.
For additional protection add a T and ball valve to the lower leg of the supply side between the main shut off and PVB about 6″ above ground. This will allow you to drain the PVB and supply side line down further.
That’s it!! You have now properly winterized your PVB. If you do not plan on watering your landscape during the winter you can leave your backflow winterized until spring. If you do water during the winter then you will perform this winterization process before each freeze. I recommend keeping your system off for the duration of winter.