A significant pressure is usually maintained in the water supply systems in order to enable water to flow normally to your home. Sometimes the water pressure may be reduced and allow polluted waters to be drawn up into the systems. Reasons for that may be technical issues or unexpectedly high water demand. The contaminated waters may enter the water supply system through points called cross connections (where potable water connects with non-potable). Examples for cross connections are some appliances like dishwashers, washing machines, sprinklers, etc. While some of the cross connections have backflow preventing mechanisms (some home appliances), others need a special device to be installed. Every state/county has codes that the residents need to follow for the installation of backflow prevention devices and their annual inspection by a licensed inspector.

Carolina Plumbing Pros can offer residents of North Carolina and South Carolina installation or replacement of the two most common types of backflow prevention devices. The double check valve (or double check assembly – DCA) is usually used on lawn irrigation systems, fire sprinklers and other systems which are not defined as a hazard. Otherwise a more reliable device may be mandated such as the reduced pressure zone device, also known as RPZD, RPZ, RPZ valve, reduced pressure principle (RP), reduced pressure zone assemblies (RPZA) or reduced pressure principle assembly (RPPA).

Both types are suitable for prevention of back pressure and back siphonage, but the reduced pressure zone device is known as more reliable because of its design. It consists of two independent check valves and a pressure monitored chamber between them. This chamber is maintained at a pressure lower than the water supply pressure by a differential pressure relief valve. Four test cocks are installed to allow an inspector to verify proper operation of the valve with a differential pressure meter. Two gate valves (one before and one after the RPZD) are provided to allow for testing and repair. Since the relief valve is designed to discharge the pressure in the drain, it’s required that the device be mounted by a professional plumber in a location where the drain won’t cause floods and damages to your home.