A hose vacuum breaker, called a back flow preventer or anti-siphone, is a device to prevent your water from getting contaminated from the other side of the hose.
A hose vacuum breaker stops back flow to the water supply by venting water onto the ground through a check valve. If the outflow pressure becomes lower than inflow pressure, a spring opens a vent to the ground.
A hose vacuum breaker should be added on each faucet connected to a drinkable water supply to prevent back flow from the other end of the hose siphoning back to the clean water if the clean water source shuts down while open.
By code, hose vacuum breakers must be installed at least six inches above the ground.
Many hose vacuum breakers have a set screw that breaks off to prevent it from being removed accidentally when the garden hose is removed. This broken screw is a problem when the hose vacuum breaker is replaced. We recommend using a hex set screw rather than the break-off screw.
You still may need freeze protection in winter.
You can test the hose vacuum breaker periodically. Just shut off the the nozzle end, turn on the water to pressurize the hose, then turn off the water. The hose vacuum breaker will spray water as the spring opens the vent to release the pressure.
Keep landscape water separate from potable drinking water. Back flow may allow fertilizers, herbicides and harmful substances to be sucked into the public clean water supply.
Back flow has two causes: back siphoning or back pressure. Back siphoning happens when water is drawn backward due to decreased pressure in the supply side of the water. Bad water may be pulled sprinklers or other emitters.
Back pressure is because system pressure is higher than the supply line’s.