How to Insulate the Backflow Preventer on a Sprinkler System

Lawn sprinkler systems work to keep your grass green and healthy, but without backflow preventers, contaminated water can get into your home's drinking water. Water is usually kept at a constant pressure that allows it to flow from the sprinklers, but contaminated water can get in when pressure changes. Pressure device assembly systems and backflow devices help keep pollutants from irrigation systems and keep potable water supplies safe. Backflow preventers can freeze when temperatures drop below freezing, though, so insulating them ahead of time is a wise idea.

In freezing weather, ice forms in standing water, and when this happens, the preventer freezes and expands, which can make it crack, warp or break. The surrounding area may flood, but the damage might not be immediately apparent. This kind of problem could end up costing you a lot of money. Though the assemblies can be turned off and drained, this means that the valves have to be set up correctly, and it has to be done each time a freeze is forecasted. This amount of work is a lot of overhead, and if you forget even once, there will be damage.

The main kinds of backflow devices are the reduced pressure zone assembly, the double check valve assembly and the pressure vacuum breaker assembly. These are all installed right after your irrigation system isolation valve. You can install your atmospheric vacuum breakers on each sprinkler zone after your zone control valves.

For reduced pressure zone valve assemblies, you can wrap your side pipes with some foam pipe wrap, R-11 fiberglass insulation or fiberglass pipe insulation and then tape them securely with heavy rubber tape. Self-stick foam insulation tape will also work, but you need to make sure that whatever kind of tape you have is waterproof.

You won't be able to wrap the reduced pressure zone valve in the center entirely, though, because you need to leave an opening there for the water to drain out from the bottom. Another way to insulate these valves is to get an open-bottom insulation pouch. These fit right over the entire assemblies and provide openings on the bottom. Attach these to the ground with stakes so they won't blow away.

Plumbers sometimes install double-check assemblies below the ground in valve boxes, which prevents them from getting damaged. If not, you can insulate these and other backflow prevention breakers in the same ways as reduced pressure zone valves.

The first step for this project is to locate the valve. Look for a valve box with a green cover; it might be hidden under some grass or soil. It could be close to your home where the domestic water main lines come into the house or near the sidewalk/street close to the water meter.

Remove the cover of the valve and turn it in quarter turns until it is not parallel with the pipe; this opens the valve. Now, you'll need to locate the pressure vacuum breaker, which should be right by your water meter. Using a flathead screwdriver, turn the two test valves a quarter of the way, ensuring the line you see is parallel with the opening. After the water flows out, turn these 45 degrees and ensure they're not entirely closed. Also, turn the valve handles 45 degrees.

You can insulate the backflow preventer with any of these methods. If you choose to get an insulating bag, be sure to measure the backflow preventer assembly first because the bag has to cover all of the handles. Also, check the R-value; higher numbers indicate more protection from the cold. It should be at least R-10 if you expect hard freezes.