RPZ/Backflow Preventer Testing

Larry’s Plumbing is a certified to test your backflow preventer and also perform your annual test and certification.



Residential or Commercial RPZ Testing A Reduced Pressure Zone Device (RPZD, RPZ or RPZ valve) is a type of backflow prevention device used to protect water supplies from contamination. RPZDs may also be known as reduced pressure principle backflow prevention devices, or reduced pressure zone assemblies.

An RPZD is considered suitable for high hazard applications, that is, where the consequence of backflow into the water supply would cause significant harm. They are considered suitable because they prevent both backflow and back-siphonage, because of a redundant design (even with two check valves broken the device still provides protection), and because they are testable to verify correct operation.

RPZD are often chosen instead of an air gap since the head loss across the RPZ is much smaller.

The device consists of two independent check valves, plumbed in series, with a pressure monitored chamber between. The chamber is maintained at a pressure that is lower than the water supply pressure, but high enough to be useful downstream.

The reduced pressure is guaranteed by a differential pressure relief valve, which automatically relieves excess pressure in the chamber by discharging to a drain. 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 RPZ) are provided to allow for testing and repair.

Almost all villages and towns in the Chicago area, require you to have a backflow preventer test
completed on an annual basis.

Larry’s Plumbing is certified to perform this service.

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f your house or business needs a required yearly test, contact us at your convenience to schedule your testing.