What Is a Vacuum Breaker?

A vacuum breaker is a device designed to prevent the backflow of water from a sewage system into a tap-water system, preventing possible contamination and a hazard to public health.

Back Siphonage

• When the pressure in a tap-water system falls, possibly because of a line breakage or pump failure, the low pressure can suck contaminated wastewater backward through the system, contaminating drinking water. This process is called "back siphonage."

Function

• Vacuum breakers are devices designed to prevent back siphonage by restoring a more standard pressure to the system or cutting off a backward-flowing current.

Atmospheric Vacuum Breakers

• Atmospheric vacuum breakers contain a floating ball that is held up by the water pressure. When the pressure falls, the ball lowers, allowing air to enter the system and cutting off any possible back siphonage.

Pressure Vacuum Breakers

• Pressure vacuum breakers contain a ball and spring. When water pressure is normal, the pressure keeps the ball from sealing the pipe; but when pressure falls, the spring pushes the ball into place, stopping the flow and preventing back siphonage from occurring.

Industrial Vacuum Breakers

• Similar devices are also used to prevent the formation of pockets of vacuum in industrial equipment. As well as back siphonage, vacuum conditions can sometimes cause damage to devices.