Now, it’s time to put the hoses back on. Trethewey uses pliers to tighten the two brass adapters, then reattaches the hot and cold water supply hoses to the threaded connections on the automatic shutoff valve.

What does RPZ stand for

Because an RPZ is designed to evacuate water, one has to concede the fact that the surrounding area will get wet. For this reason alone, a RPZ should not and cannot be installed inside a structure. In this picture, the RPZ was installed in a mechanical room. Notice the electrical panels! The plant moved the enclosure outdoors when someone determined this was a dangerous location for the RPZ. Read more about this installation here.

Incorporating these precautions can prevent any accidents or damage during installation. It’s also beneficial to inform anyone in the household about the ongoing work to avoid disturbances.

RPZ Valve price

If you haven’t read our brief post on the differences between DC and RPZ backflow preventers, take a moment to familiarize yourself with their distinction.

Reduced Pressure BackflowPreventer Test Procedure

A backflow enclosure provides excellent protection against theft and vandalism, not only because of its durability of the enclosure, but also because the device is hidden from view. If an RPZ was to discharge water, backflow enclosures provide visible means to detect it. If the RPZ were dumping water inside a building, water would rise until someone entered the mechanical room, or until the damage was so great it surpassed the mechanical room. A heated backflow cover is a perfect place to install the RPZ, protecting the public water supply and protecting the building from water damage.

RPZ diagram

Many automatic shutoff valves come in a kit that can connect to the existing valve with adapters. Trethewey temporarily installs the brass adapters on the existing shutoff valves and inserts 1/2-inch PVC piping into the ball swivels inside the adapters. Then, he attaches 1/2-inch PVC elbows to the brass connections on the underside of the automatic shutoff valve.

2" rpz

As with any other piece of equipment, it’s best to understand how the RPZ backflow preventer works in order to determine how to install one for ideal use and function. Sadly, many mechanical or plumbing engineers don't spend much time thinking about the backflow preventer during the project design phase and, in many cities across the country, the backflow preventer is installed inside the building.

RPZ valve how it works

With the increasing requirements nationwide for RPZ installation, it’s also important to think about where it should be installed. There are two options: inside in a mechanical room or in an RPZ backflow cover.

The automatic valve Trethewey uses has a leak sensor that goes on the floor behind the washing machine to detect moisture. He plugs it into a designated port and places the sensor in a strategic spot, close enough to detect even minimal water presence.

Automatic shutoff valves can be bulky, so they commonly have space for fasteners. Trethewey makes two marks on the wall over the outlet box, predrills the holes, inserts hollow-wall anchors, and attaches mounting screws to secure the valve assembly in place.

First, Trethewey closes the hot and cold water shutoff valves that supply water to the washer and disconnects the supply hoses from the valves with pliers. It’s best to have a rag ready so you can catch any water that spills from the hoses.

RPZ vs double check

The automatic shutoff valve has both a power cord for the wall socket and its own receptacle on the front face. When Trethewey plugs the washer’s power cord into the valve, it ties the valve’s position to the washer’s power draw. A light on the valve lets him know the valve is ready to work.

The RPZ will absolutely protect the public drinking water supply, but if installed in the wrong space, it can potentially cause flood damage to the building. It is important to use best practices when installing an RPZ, and the best place for installation is outside in an RPZ backflow cover.

Rpz meaning plumbing

Backflow enclosures made to these standards also provide easy access for maintenance and repair. The materials used for RPZ enclosures are designed to withstand the elements and are tested for structural strength as well as security.

Trethewey can now hold the valve assembly against the wall and mark where to cut the straight piping so the valve fits just outside the outlet box.

An automatic washing machine shutoff valve gives you an extra layer of protection against flooding and water damage. It detects when you’re actively washing clothes and only allows water to flow when the washer has a cycle running. Modern versions of the device can even detect leaks and shut off the water supply in advance. In the above video, This Old House plumbing and heating expert Richard Trethewey shows how to install one for added peace of mind—and potentially even lower insurance premiums. Learn more in our guide below.

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Finally, Trethewey reopens the water supply and starts a test cycle for the washer. A light on the valve indicates that the washer is on. If the pressure on the hoses releases when he pauses the fill, the installation is complete.

Once Trethewey has the measurements and marks he needs, he uses a tubing cutter to trim the pipes to the correct length. Then, he cleans the cut ends and the inside of the elbows with PVC primer.

This short video shows an RPZ inside an enclosure in action. The relief valve discharge rate charts for a popular backflow preventer manufacturer indicate an RPZ can discharge an incredible amount of water in a very short amount of time. Here’s an example of how much water dumps from this small-diameter RPZ!

To see how the RPZ works in various situations, including illustrations and demonstrations of an RPZ in action, here’s a short video.

Have a question about a backflow preventer enclosure?Click the contact us button below and one of our experts will be able to help with your specific enclosure needs.

Backflow preventers work by letting water flow through them in one direction, but prevent water from flowing back through them in a reverse direction, protecting the water supply. A commercial building or industrial plant can use all the water it wants, but once the water has passed through the meter and the backflow preventer, it will not be allowed back into the water supply. An RPZ provides the best level of protection because of its relief valve, which will open up and dump the water as a last resort to prevent contamination.

Backflow enclosures were designed with RPZ installation in mind. ASSE 1060 regulations ensure that backflow enclosure manufacturers are designing their products with function and safety in mind. ASSE 1060 testing strictly requires that backflow enclosures provide a drain for when the RPZ inevitably dumps water. For backflow preventers sized 4" and larger, the drain must be able to move 710 gallons per minute.

In response, there is a growing trend across the country where water jurisdictions are requiring the use of an RPZ backflow prevention assembly. In fact, many areas are now requiring the RPZ on all domestic and fire service lines. So, even if you’re in an area where single checks or double checks were once acceptable, that could change, if it hasn’t already.

After everything’s primed, Trethewey uses PVC cement to join the pipe assemblies together, following the manufacturer’s instructions.

The RPZ clearly indicates whether the valve is working properly or if service is needed. If no water is dumping out of the relief valve, the backflow preventer is operating as intended. If the relief valve is dumping water or spitting out water of any amount, maintenance is required. This clear indication of a system issue is why more and more municipalities across the country are requiring the RPZ for both domestic and fire lines.

Reduced pressure zone (RPZ) backflow assemblies are extremely important. They’re used to keep contaminated water out of the public supply and provide the highest level of protection.