Why RPZ Valves Are Required and How To Install One

RPZ backflow preventer.png

Reduced pressure zone (RPZ) valve assemblies are extremely important; they keep contamination or pollution out of your water. Specifically, an RPZ is installed onto a plumbing system to protect both your drinking water and the water supply at large.

RPZ valves provide the highest level of protection for the water supply. That’s why municipalities and engineers across the country are increasingly requiring these types of backflow prevention devices for new construction. In fact, many communities now mandate their use on all domestic and fire service lines. If you live in an area where single- or double-check (DC) valves are acceptable, with their low-level hazard protection, that may soon be changing. Always check with your local governing authorities to stay up to date on codes and compliance.

Let’s take a look at why an RPZ is safer and how to install one.


An (RPZ) lets you know the valve is functioning properly. RPZ backflow preventers consist of two independent check valves. They work like a DC backflow preventer, but they also have an intermediate relief valve that opens to the atmosphere if both check valves fail.

If you walk up to an RPZ and no water is dumping out of the relief valve, you know the backflow preventer is working properly. If the relief valve is releasing any amount of water, something is malfunctioning and maintenance on the valve is required. The peace of mind and quick check ability RPZs provided is why municipalities and engineers are requiring them as part of a larger approach to protecting our delicate water supply.

Backflow preventers, as the name implies, work by letting water flow through them in one direction, preventing water from flowing back through them. A house or business or cyanide plant can use all the water it wants, but once the water has passed through the backflow preventer, it will not be allowed back into the water supply. An RPZ provides the best level of protection because it has a built-in relief valve, which will open up and evacuate any backflowing water. You can read the details about the differences between DC and RPZ backflow preventers here.

wilkins discharge rates for rpz valves.pngWhat About RPZ Installation?

Now that RPZs are more commonplace, you may need to know how and where to install one. There are two options: inside a mechanical room or in an RPZ enclosure.

Because an RPZ is designed to dump water, the surrounding area will get wet. An RPZ that is dumping water is working exactly how it’s supposed to. Unfortunately, this is not a good situation if the RPZ is installed inside a vault, mechanical room or in a utility closet as it will damage any and everything around it. At Safe-T-Cover, we've seen these devices installed in ceilings and attics!

An RPZ can discharge a significant amount of water in a very short amount of time. To the point, review this flow rate chart for a popular backflow preventer manufacturer.

The RPZ will absolutely protect your water supply, but if installed in the wrong space, it will absolutely destroy your property. It is important to use best practices when installing an RPZ, and the best place for installation is outside in a rated, insulated RPZ enclosure.


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Our enclosures were designed with RPZ installation in mind. ASSE 1060 regulations ensure that backflow enclosure manufacturers design their products to specific standards. ASSE 1060 testing requires enclosures provide a drain for evacuated water, and these requirements for drainage are strict. For backflow preventers sized 4" and larger, the drain must be able to move 710 gallons per minute. Enclosures made to these standards also provide easy access for maintenance and repair. Materials used for RPZ enclosures must be designed to withstand the elements and are tested for structural strength as well as security.

An aluminum enclosure is excellent protection against theft and vandalism, not only for durability reasons, but because the device is hidden from view. If an RPZ was to discharge water, enclosures provide means to detect it without exposing the equipment. If the RPZ were inside a vault dumping water, you wouldn't know until someone entered it, or until the damage goes well beyond it. A heated enclosure is the perfect solution for installing your RPZ above ground, providing the highest levels of protection for the water supply and protecting the surrounding area from water damage, while also guaranteeing proper function in all weather conditions.

If you’d like more information or tips on how to design your enclosure, we can help. Download our guide 5 Design Guidelines and 25 Application Tips. Inside this complimentary resource, you'll find everything you need to ensure your RPZ valve is installed correctly and provides your property and your water supply maximum protection.

aluminum enclosures

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