Will Sprinklers Work With No Backflow Cap?

What a Backflow Device Does

• Backflow devices consist of either a vacuum breaker or a check valve. The check valve is usually installed underground and has a flap within the valve that moves only in one direction. This flap allows water to flow into the sprinkler lines, but prevents it from flowing back into the main water line. A vacuum breaker is the more common type of backflow device. These breakers are installed above ground and rely on atmospheric pressure and water pressure to keep water moving in one direction only. Pressure vacuum breakers consist of internal parts that include a bonnet, O-ring and cap. These pieces work together to produce a vacuum seal at the base, which allows water to flow in one direction.

How the Cap Works

• The cap on a pressure vacuum breaker holds down all the other internal components. The cap is attached to the breaker via a single screw or nut. This screw or nut is anchored to a small pole inside the breaker that is welded at the bottom. Caps are made out of brass to be highly resistant to rust and corrosion. Some models of vacuum breakers have threaded caps, which attach to the base by screwing the entire cap onto the O-ring assembly.

Effects of Removing the Cap

• Because pressure vacuum breaker caps hold down all the internal pieces that create the vacuum seal within the device, the cap must be securely in place for the breaker to work correctly. Not anchoring the cap to the base properly will result in spraying water from around the O-ring. The cap may also blow off under heavy water pressure, causing a potential safety hazard. It's critical that the cap be in place and tightened as securely as possible.

Repairing Backflow Damage

• If the cap to the vacuum breaker is cracked, dented or otherwise damaged, it must be replaced with a new one. If the internal components of the breaker fail due to frozen water lines, they can be replaced with a standard breaker repair kit. Replacement caps are not available in most vacuum breaker repair kits, and generally must be ordered from the manufacturer. Other parts of a breaker, including the heavy brass frame and ball valves, must be replaced with an entirely new unit as they are often welded together into a single part.