A RPZ refers to a reduced pressure zone and applies in any discussion about reduced water pressure situations in a disruption of the water supply.  Where a RPZ occurs, a RPZD, or reduced pressure zone device, is needed to prevent back pressure, or back-siphonage, from occurring.

A RPZ is a redundant design, providing several safety features so that if one fails there is still a backup to do the job.  Most RPZs consist of two independent check backflow valves with a pressure chamber between them.  The chamber keeps a pressure that is lower than the water supply pressure but high enough to do the job downstream.  The reduced pressure is maintained by a differential pressure relief valve which automatically relieve excessive pressure in the chamber.

A RPZ is easily testable to verify correct operation because of four test cocks installed in the RPZ D which allow a backflow inspector to verify proper operation of the valve.  There are two gate valves which allow for testing and repair of the RPZD.

A reduced pressure zone device is tested with a device known as a differential gauge.  This gauge uses a hose attached to test cocks of the RPZD and it checks to make sure the check valve springs and the relief valve springs are working properly.

Buildings where constant water pressure is necessary and required must install two RPZDs to that one is always functioning should the other fail.  That way there is never any danger of backflow occurring and thus the water supply will remain contaminant-free.

As mentioned in earlier articles, backflow occurs when the water pressure entering a building suddenly decreases. This can happen because of a broken water main or even a fire requiring copious amounts of water to extinguish.  When water pressure suddenly drops, the direction of water in the pipes can reverse, meaning contaminated water from a building can flow back into the main city water supply.  Obviously this must be avoided and thus the need for RPZDs.

Several states now require that RPZDs are tested annually by a certified and licensed backflow testing company.  Texas is one such state that requires this annual backflow testing.  City Backflow Testing is certified with the state of Texas for backflow testing and maintenance, and only uses the best in backflow preventers to assure that you will never have to worry about a contaminated water situation due to backflow.  Remember the name, City Backflow Testing, the next time you need maintenance or testing.