THE SAFE-T-COVER BLOG

How Does a Backflow Preventer Work?

It's important to understand how a backflow preventer works. If you’re like most of the plumbing engineers we’ve talked to over the last three years, you probably don't spend much timing thinking about the placement of the RPZ backflow preventer during the design of the project. Your firm has been specifying the valve indoors for many years and why make a change, right? Here’s the problem. That the way the RPZ valve works is that it is designed with a relief valve that opens if either of the check valves fails. What that means is water is dumped in the building until the problem is detected and resolved. In the meantime, your design decision to place the RPZ backflow preventer inside the building has resulted in a flooded building and more than likely your client and their insurer may be asking this question – why?

A Common Occurrence 

This video below shows how an RPZ valve works when installed outside of a building in an ASSE 1060 approved backflow enclosure. While some may think something is wrong with the valve, it is actually doing its job. Here's an in depth explanation of how an RPZ backflow preventer works as opposed to a double check backflow preventer. More than likely construction in the area caused debris to get up in the valve causing the RPZ relief valve to open. We just happened to be driving by and noticed water pouring out of the enclosure. We stopped, removed the access panel and shot this short video.

You may be surprised to learn how often this happens. At Safe-T-Cover, we typically get 2-3 phone calls per month from a worried passerby. All they can see is water gushing out of our boxes so they call us worried our equipment has failed. It hasn't, it's just the RPZ inside doing its just and protecting the water supply from backflow.


Find your RPZ enclosure here


Unknown Risk

In the last three years STC has made presentations to hundreds of civil, plumbing, and mechanical engineers across the country. During these presentations we learned most designers just aren’t aware the relief valve could dump large volumes of water into the building. And those that did were incorrectly assuming the drain installed below the valve would be sufficient. This lack of awareness puts the building at risk of flooding if the relief valve opens.

Changing Standards

More and more water jurisdictions across the US are requiring the use of the RPZ instead of the double check. An RPZ valve offers better protection to the water supply. With this added protection comes the additional work of specifying and installing reduced pressure zone valves in a safe place. For those assuming the drain below the RPZ is sufficient, check out what a member of the Chicago ASPE Chapter, David DeBord, said in an article in 2013 “The floor drain capacity required for RPZs 3” diameter and larger are likely to be cost-prohibitive due to necessary pipe diameter and fall rates.” You can read the full article here.

Increase Awareness, Improve Safety

Now that you’ve seen the footage of the RPZ device doing what it is designed to, pouring water, what can you do differently? An option would be to move the backflow design to the scope of the civil engineer on your upcoming projects. If the RPZ valve is installed outside the building, you no longer have the design risk associated with the RPZ backflow preventer flooding the building. See page five of this catalog from Zurn, a backflow preventer manufacturer, for examples of where they expect backflow devices to be installed. Another option is to share this information with your colleagues to raise the awareness. As the RPZ is required by more and more water jurisdictions, the need to understand how it works and the risks associated with its placement become more and more important.

New call-to-action

Related Posts

How Does an RPZ Work?

3 Reasons Why a Backflow Cover Must Have Heat

From the Field: Tips for Safe-T-Cover Enclosures and Protective PVC Coating

Why RPZ Valves Are Required and How to Install One

DC VS RPZ - WHAT'S THE DIFFERENCE?

From the Field – National Backflow Prevention Day

Forward thinking in Arlington, Texas: Leading the way with public health and backflow preventers

Why Should I Mount my RPZ Backflow Outdoors?

What’s in Your Meter Vault?

Three Different Types of Reduced Pressure Zones — Which One Meets Your Needs?

The Safest Place for a Backflow Preventer Installation

Installing Fire Dept Connection & Backflow Prevention Valve for Safety

The Dangers of Backflow – Corpus Christi, TX

The Drawbacks to Using a Backflow Cage

29 Weeks and Counting

Quintessential List of Backflow Preventer Enclosure FAILS

Chicago Backflow Incident of 1933

Three Reasons Why You Should Choose an N-Type Device

IoT Takes Backflow Prevention To Another Level

The Right Backflow Insulation Cover & Heater For You | Backflow Cover

A Manufacturer Shares A Warning About RPZ Backflow Preventers

How RPZ Backflow Preventers Protect Drinking Water

This is How You Cut Backflow Preventer Installation Costs

This is How A Backflow Preventer Installation Should Be Done

Part 3: Why You Should Keep Backflow Preventers Out of Basements

Above-Ground-Backflow Assemblies Are a Big Winner in Las Vegas

A Backflow Preventer in a Utility Vault Can Be Deadly

How to Find the Perfect Enclosure for Backflow Prevention

How to Decide If You Should Repair or Replace Your Backflow Preventer

VIDEO: Safe-T-Cover Hopes To Change The Way You Think About Backflow

What You Need to Know About Backflow Prevention and Flood Risks

How To Ensure Your RPZ Enclosure Provides Maximum Protection

What is a Cross Connection Control and Backflow Preventer?

CONTAINMENT VS ISOLATION: THE COMMERCIAL BACKFLOW PREVENTER INSTALLATION BATTLE

Fields Presents a "Smart" Future for Backflow Preventers

Water Quality Drops When Backflow Preventers Fail

Backflow Prevention Plays Small but Mighty Role in Water Quality

When You Should Use Backflow Theft Prevention Cages

Cross Connection Control Spotlight: How LVVWD Avoids Backflow

Backflow Protection and Fire Protection Pit Safety Against Safety

Backflow Testers Provide Critical Link in Water Quality

What we Learned About Underground Backflow Preventers During the Panel

Still Spec'ing the Watts 909? 3 Reasons to Switch to a 957 Assembly

Something to Consider with Outdoor Pump Covers on the Roof

Never Put Your Backflow Preventer Installation In The Basement

What Monitoring Systems are Available for My Valve and Pump Heaters?

See For yourself - Utility Vaults Flood (All the Time)

AMI Water Meters Allow Utilities to Provide Higher Level of Service

Can you have a Fire Department Connection on an Enclosure? Yes! It's a Safe FDC Location

Roswell, GA Updates Standard Details For RPZ Backflow Preventers

How to design & Buy a Pump Enclosure

Get the free, editable checklist.

download-cta
DOWNLOAD NOW

CONTACT US

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.