The Safe-T-Cover Blog

Using Utility Vaults for Backflow Preventers– Is This a Problem

Posted by Craig Carmon on May 25, 2017

None of us like change. I get it. Especially when there’s no need to change. After all, “if it ain’t broke don’t fix it”, right?

But what if you learned it just may be broken. Maybe the evidence you read here causes you to wonder if it is broken. And if indeed it is broken, then clean drinking water is at risk. If the drinking water is compromised with a backflow incident which causes illnesses or even deaths, a lawyer will be at work determining who pays the bill.

We’ve spent the last few years learning about backflow design all over the United States by meeting with water jurisdictions and civil engineers. We’ve talked with backflow device manufacturers, trade groups including ABPA and AWWA, and listened to what USC’s Foundation for Cross-Connection Control and Hydraulic Research has to say on the subject. We've come across two compelling reasons which, in our opinion, constitute a problem. You may find you agree.

A flooded vault creates a potential cross connection

Water jurisdictions often tell us they know a vault can flood. In February of 2017 Safe-T-Cover hosted a webinar for water jurisdictions and webinar 2-2017 poll 1.pngengineers during which our speaker discussed vault flooding. Partway through that segment, we ran a poll asking the audience if they were aware that utility vaults are prone to flood. As you can see in the graph, about 70% said yes. Some water purveyors say at least half the vaults they look at have water in them. A Texas backflow tester has sent us many pictures and videos of flooded vaults over the years. We also interviewed a tester and instructor who works in Virginia on the subject, Chris Mayhew, to hear what he had to say about it. To save you the click, here was the most staggering thing he told us, "Except for brand new installations, 100% of vaults I've worked on have flooded at least once. " A cross connection control investigator in a large mid-western city told us from the thousands of vaults he opened over a 30 year career that about 1 vault out of 100 is dry. He also said that most of the time the backflow device was completely under water. Long-time respected voice in the backflow industry USC's FCCCHR has written about vault flooding three times in their publication, Cross Talk. The first was in Summer of 2005 when they said,

"The Foundation would like to recommend that all backflow prevention assemblies be installed above grade. There have been instances where double check valve assemblies have been installed below grade to prevent freezing and they have ended up completely under water due to a flooded vault. In other cases they have become completely buried because of mud filling in the vault during a rainy season."

You can read the full article on pages four and five by clicking here. Then again in Spring 2014 they stated,

"The DC and RP must be installed between 12” and 36” above grade...When a backflow preventer is installed below grade, the vault or pit in which an assembly is installed may fill up with water—possibly contaminated water. The water in the pit could create a cross-connection between the water in the pit and the backflow preventer through the test cocks. This may occur whether the testbackflow-preventer-vault-flooded.jpg cocks are opened or closed."

This statement brings to light why a flooded vault is such bad news. It can cause a cross connection when the entire purpose of installing a backflow preventer is to eliminate cross connections. You can read this article which starts on page 1 by clicking here. Finally, in the Winter 2016 edition they wrote,

"The Foundation recommends assemblies be installed 12” to 36” above grade. If an assembly needs to be hidden from view for aesthetic reasons, consideration should be given to installing it behind a wall or landscaping. For freeze protection or the threat of vandalism think about installing an assembly in an enclosure instead of a pit or vault. In some cases, an RP is replaced with a double check valve assembly (DC) since the DC has “no openings,” therefore reducing the risk of a cross-connection. Yet, the test cocks found on the DC could be the site of a cross-connection. If a test cock leaks or is broken off and becomes submerged backflow could occur through the test cock. So, instead of preventing backflow; a cross-connection has been created through the assembly. "

You'll find the entire article on page 3 by clicking here. Additionally, most states require each water jurisdiction to have in place a cross connection control program with language similar to this – Each public water supply shall develop a comprehensive, ongoing program for the detection, elimination, and prevention of cross connections. If vaults can create a cross connection, how are they in compliance with this requirement? Knowing this, why would the vault ever be an acceptable design if the responsibility is to provide a design that prevents cross-connections and safeguards clean drinking water? For more visual proof of how often vaults flood, watch the video below for footage sent to Safe-T-Cover by testers.

Watch the vault panel discussion webinar video featuring three industry experts

A vault is a confined space, Which cause 92 Deaths Per Year

According to OSHA, water utility vaults or pits are considered a confined space. Here is the definition from their website,


"Many workplaces contain areas that are considered "confined spaces" because while they are not necessarily designed for people, they are large enough for workers to enter and perform certain jobs. A confined space also has limited or restricted means for entry or exit and is not designed for continuous occupancy. Confined spaces include, but are not limited to, tanks, vessels, silos, storage bins, hoppers, vaults, pits, manholes, tunnels, equipment housings, ductwork, pipelines, etc."

Most vaults are not what are called "permit required" confined spaces, however, the municipality can put that into their local code which would then require workers to have a permit to open them and also may require signage. When a backflow in a vault is tested each year, the tester must climb down into this confined space. According to the national institute for occupational safety and health, an average of 92 fatal injuries occur each year in confined spaces. You might be thinking, "these testers are trained professionals, surely they know how to manage a confined space." That’s a good observation. But what about the building's maintenance person, property owner, or the adventurous kids that can get in the vault by merely opening the lid. We have never seen confined space danger signs posted at or on the vault. Testers agree that there is little stopping curious people from opening them up. Vaults do have a locking mechanism, but apparently many are damaged within a couple years.

There are two key reasons engineers and water districts site for installing backflow preventers in vaults - heating, and aesthetics. There are industrial-enclosure.pngthree options all with their own pros and cons for keeping pipes warm through the winter - vaults, enclosures, and buildings. We suggest an enclosure for freeze protection, and if you clicked the links above and read the articles from USC, you'd see their opinion as well. Here is part of the article from Winter 2016 again, "For freeze protection or the threat of vandalism think about installing an assembly in an enclosure instead of a pit or vault." In terms of backflow enclosure aesthetics, all you require is strategic placement on the grounds and possibly some landscaping. Placing the device behind a wall or among hedges is an easy way to keep the property looking nice. There are also options regarding the enclosure itself in terms of size and color. Depending on the property, a green or tan enclosure can blend in. Knowing this, why would you continue to design a vault for the backflow when an above ground enclosure is an already accepted design in most major cities across the US?

Is there a problem?

We see this as a clear problem but know the utility vault has been the standard for backflow design for several decades. Yes, we know change in any industry can be hard. But we believe the protection of clean water, safety, and the owner’s best interest should be enough evidence that the best practice of using an above ground enclosure should replace the vault. It seems we aren't the only ones. See page five of this catalog from Zurn, a backflow preventer manufacturer, for examples of where they expect backflow devices to be installed. The civil engineering community has implemented many other changes through the years when a better design presented itself. Your next project is the time to make this change. Please call us if we can provide support or help you on your next project.

watch the vault panel webinar recording with captions

Topics: Backflow Preventers, vaults, Civil Engineering, Safety