The PVB includes a check valve which is designed to close with the aid of a spring when flow stops. It also has an air inlet valve which is designed to open when the internal pressure is one psi above atmospheric pressure so that no non-potable liquid may be siphoned back into the potable water system. Being spring loaded it does not rely upon gravity as does the atmospheric vacuum breaker. This assembly includes resilient seated shut-off valves and testcocks. The PVB must be installed at least twelve (12) inches above all downstream piping and outlets. The PVB may be used to protect against a pollutant or contaminant, however, it may only be used to protect against backsiphonage. It is not acceptable protection against backpressure.
Seen on: lawn irrigation systems having intermittent use
This assembly consists of two internally loaded independently operating check valves and a mechanically independent, hydraulically dependent relief valve located between the check valves. This relief valve is designed to maintain a zone of reduced pressure between the two check valves at all times. The RP also contains tightly closing, resilient seated shut-off valves upstream and downstream of the check valves along with resilient seated testcocks. This assembly is used for the protection of the potable water supply from either pollutants or contaminants and may be used to protect against either backsiphonage or backpressure.
Seen on: High hazard systems such as lawn irrigation, boiler makeup, chiller makeup, and domestic water
The Double Check Valve Assembly consists of two internally loaded, independently operating check valves together with tightly closing resilient seated shut-off valves upstream and downstream of the check valves. Additionally, there are resilient seated testcocks for testing of the assembly. The DC may be used to protect against a pollutant only. However, this assembly is suitable for protection against either backsiphonage or backpressure.
Seen on: Low hazard fire protection systems
Out of sight, all water pipes entering your home, the restaurant down the street, and your local hospital, are all connected to the same water supply. In your residence or business, any mechanically-controlled use of water (ie: lawn irrigation, fire sprinkler system, pop machines, pedicure bowls, etc.) a backflow preventer is a necessary accessory to your plumbing system. A “backflow preventer” is just what it sounds like. Once water pressure drops, the backflow preventer seals shut, not allowing any water to flow backwards in the wrong direction.
The EPA mandates that all backflow preventers be tested and certified once, sometimes twice per year, depending on the geographical location of the backflow preventer. If a water customer chooses not to meet this requirement, that customer will eventually be faced with the termination of their water service until they are able to show proof that their device has been properly tested and maintained. This annual or semi-annual testing is what ensures the safety of your drinking water.
When there is a sudden drop in water pressure in your area (usually during the elimination of a fire, or concurrent use of large amounts of water by too many people at one time) the drop in pressure is what then pulls water that has already been expelled back into the main water supply.
Simply put: “Used” water is pulled back into the main water supply.
Technically: Water that has left the main water supply, then entered into your home or business to intermingle with numerous contaminents is no longer safe for drinking. Once this water is pulled back into the pipes in the wrong direction, it has the opportunity to mix with the clean drinking water, thus contaminating the entire town’s water supply.
Water that is safe for human consumption (meets the Safe Drinking Water Standards) and is aesthetically pleasing.
The use of assemblies, devices, methods, and procedures to prevent contamination or pollution of a potable water supply through cross-connections.
Any arrangement of pipes, fittings, fixtures, or devices that directly or indirectly connects a non-potable water system to a potable water system.
A mechanical device used to prevent the backward flow of contaminants or pollutants into a potable water distribution system.