Winterizing Your Above Ground Backflow Preventer

This part of Texas has mild winters, but we do get freezes. You need to protect your above ground backflow preventer when the temperature drops below 32°F so that trapped water doesn’t freeze, expand, and damage the device.

The Importance of a Backflow Preventer

The Texas Commission on Environmental Quality (TCEQ) Code Rule 344.50 states, “Any irrigation system that is connected to a public or private potable water supply must be connected through a commission-approved backflow prevention method”. The rule also lists the different types of backflow preventers that are permitted under certain conditions.

All irrigation system backflow preventers have the same purpose: to keep water flowing in one direction and to prevent contaminated water in the irrigation system from reversing and entering your family’s potable (suitable for drinking) water supply and the city’s water supply.

Irrigation water is a contaminant (creates a health hazard) and not just a pollutant (objectionable in odor or color). Toxic chemicals (fertilizers, pesticides, etc.) and animal waste can flow back up your irrigation pipes and into your drinking water if not prevented. The valves that turn your irrigation system on and off are not adequate to stop a backflow. They can be open when the backflow occurs (your sprinkler system is on), or they can break or leak, which is why a backflow preventer is vital to protect you. Many of the automatic valves, such as the electric solenoid valves, don’t stop backflow even when fully closed and “off”. They are directional in design, and when a backflow occurs, they will open slightly.

How do backflows occur? Normally, the water pressure in the home’s water supply keeps the irrigation water from going backwards. However, if the pressure drops suddenly, this could cause a negative pressure in the home’s main supply. Negative pressure creates a siphoning effect, causing the water to flow backwards. Although such events are rare, water can be sucked out of sprinkler lines into the main water supply, and from there into household plumbing fixtures, such as bathtubs, sinks, showers, tubs, toilets, and faucets. This can happen when your water company shuts off the water for repairs, or installs a new pipe. Fire fighters pumping water out of fire hydrants can cause water pressure in nearby areas to drop, creating a backflow in those areas.

Winterizing an RPZ (Reduced Pressure Zone) Backflow Preventer

1. Shut off the isolation valve. This valve is usually found in the ground inside a green colored valve box, either close to the backflow device or the water meter. The isolation valve needs to be “freeze proof” — either below the frost line, or wrapped with insulation.

2. If you have an automatic controller, turn it to the “off” or “rain” mode position, shutting off signals to the valves so they don’t come on. The controller will continue to keep time, and your programming won’t be lost. It’s a wise precaution to shut off the power to the controller if a pump is wired to it. The pump could get damaged if, by a remote chance, the controller started it when the system was shut off. When you start up the system again, you’ll have to reprogram the time, and possibly your settings. Mechanical controllers use more electricity than the automatic ones, so turn off their power to save electricity. You have no settings to lose in this case.

3. Remove the dust caps from the four test cocks on the RPZ.

4. Take a small flat-head screwdriver and turn the screw in the center of each test cock to a 45 degree angle, opening up the test port. Water may shoot out with some pressure, and drip for a short time. Leave the screws at 45 degrees, which is the halfway off position. Any water left in the device should evaporate, so there isn’t any left inside to freeze and cause damage.

5. Next, turn shutoff #1 and shutoff #2 handles to a 45 degree angle or the halfway off position. This prevents water from being trapped in the shutoffs and causing freezing damage to them (never leave the shutoff handles in the fully open or closed position when freeze protecting your device).

6. Loosen bolts on the relief valve cover until the water drains.

7. Insulate the RPZ by wrapping the device in foam pipe wrap, followed by a heavy rubber tape to protect the insulation. Then cover the backflow device with an insulation bag.

8. If you wish to run your system once the freeze is over, remove the insulation bag, and open the isolation valve. Water will shoot out of the device test ports, allowing any air or debris to escape. Next, close the test cocks with a screwdriver (screw slots vertical). This will stop water spraying out of the backflow preventer. Turn the #1 and #2 shutoff valve handles to the fully open position. Tighten the bolts on the relief cover. You can keep the insulation on all winter (except for the insulation bag when running the system). Set your controller.

To properly winterize your backflow preventer you must have an isolation valve. For new irrigation systems the Texas Commission on Environmental Quality (TCEQ) Code states, “All new irrigation systems must include an isolation valve between the water meter and the backflow prevention device”, Rule 344.62.  If you have an older system and don’t have an isolation valve, leave the backflow device on, and properly insulate it for a freeze. Call us and we’ll install one for you so you can winterize your device in the future. We’d also be glad to help you with the winterizing.

Winterizing a Double Check Backflow Preventer

In central Texas most double check backflow preventers are installed underground, and are therefore insulated from freeze damage. For winterization of above ground double check devices, follow the RPZ steps (except for the relief cover — the double check backflow doesn’t have a relief valve).

Winterizing a PVB (Pressure Vacuum Backflow) Device

1. Shut off the isolation valve.

2. If you have a controller, set it to the “off” or “rain” mode position.

2. Locate the two test cocks used to test or drain the main cavity of the backflow device. Take a small flat-head screwdriver and turn the screw in the center of each test cock one quarter of a turn (45 degree angle) to open them. Water may shoot out with some pressure, and drip for a short time.

3. Turn the #1 and #2 shutoff handles to a 45 degree angle or the halfway off position. Keep them in this position until you’re ready to start your system again.

4. Insulate the device in foam pipe wrap, and use a heavy rubber tape to protect the insulation. Cover the device with an insulation bag.

5. To run your system again, remove the insulation bag and open the isolation valve (water will shoot out of the test cocks). Close the test cocks by turning the screw in the center to the closed (screw slot vertical) position. This will stop the water from spraying out of the backflow device. Turn the #1 and #2 shutoff handles to the full open position (handles in line with the flow of the pipe). You can keep the insulation on all winter (except for the insulation bag when running the system). Set your controller.

You should use your controller to help drain the system during the winterization process.  To do this, turn on the lowest elevation zone on the controller and let it run.  Then turn off the isolation valve and drain the unit.  When those steps are complete, turn the controller to the “off” position.

Would you like some help winterizing your system?  We are the experts in irrigation and sprinkler repair, restoration, and maintenance.  Call us today at (512) 534-7449.