How RPZ Backflow Preventers Protect Drinking Water

RPZ backflow preventers are the best protection you can buy, especially for high-hazard applications like irrigation systems. In general, irrigation systems require an RPZ device because they can come into contact with fertilizer and pesticides.

Let’s take a closer look at reduced pressure zone assemblies, what they do, and why they’re so important. 

What RPZ Means 

RPZ stands for reduced pressure zone. An RPZ lets you know that the valve is working properly. RPZ backflow preventers consist of two independent check valves. They work like a double-check backflow preventer, but they also have an intermediate relief valve that opens to the atmosphere if either check valves should fail.

Backflow preventers work by letting water flow through them in one direction, but they prevent water from flowing back through them in a reverse direction and causing a cross-connection. 

For these reasons, RPZs are being required across the country.  An RPZ provides the best level of protection because it has a built-in relief valve, which will open up and actually dump the backflowing water out of the valve in order to prevent any chance of contaminated water re-entering the water supply. The water only dumps if there is a problem with one of the check valves or relief valve. 

How to Test a RPZ

How to Install a RPZ Backflow

RPZ Backflow Preventers Bringing About Change

Municipalities that are updating their standard details and local codes to conform with recommended best practices include:

  • Fort Worth, TX
  • Lynchburg, VA
  • Delaware, OH

These new standard details typically not only require the use of an RPZ device but that the device must be tested once each year. Once the RPZ is tested, the certification paperwork is forwarded to the city.

Because of the fact that RPZ backflow preventers release water (and lots of it) when they’re working properly — they can cause floods. The floods can cause massive damage depending on where the devices are installed. That’s why more and more RPZ backflow preventers are being installed outside and above ground, in a backflow enclosure. Oftentimes, RPZs are installed in a basement or somewhere else inside the building (like next to the mechanical room) and when RPZ releases the water, everything near it will get wet.  

Where to Install an RPZ Backflow Preventer

There are basically two options for where to install an RPZ Backflow Preventer. Those options include inside in a mechanical room or in an RPZ enclosure.

Because an RPZ is designed to dump water, the surrounding area is going to 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 mechanical room or in a utility closet as the surrounding area will be damaged by the water pouring out of the backflow preventer.

We strongly recommend installing outdoors and above ground inside an ASSE 1060 compliant RPZ enclosure.

It’s Time For Change

If you’re an architect or design engineer, you should consider the evidence when looking at the different types of backflow prevention devices. Why take the risk of installing the RPZ inside the building? There’s nothing to gain.

You don’t have to go with the status quo on your next project for an RPZ backflow device design. You can decide to keep the best interest of your client in mind and move it outside and above ground. 

More and more municipalities and water purveyors are evolving their standards for backflow prevention valves on commercial facilities. To find out the latest trends in backflow prevention, check out our guide “Trends in Backflow Preventer Valve Specification and Location.” You’ll find valuable information on everything from types of backflow prevention devices to common installation locations. 

Best Practices in Backflow Prevention & Protection

Topics: RPZ Flooding


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