During one of our webinars on backflow installation and waterworks best practices, water purveyors and design engineers asked us so many good questions that we decided to gather the answers into this post.
Here are what cross connection control managers and civil engineers across the country want to know about backflow prevention, backflow prevention devices and best practices to safeguard the water supply.
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If everything is going well, not often. However, each water authority has to follow and enforce regulations as well as stay up-to-date on best practices.
Backflow events unfortunately take place all the time. It's not something that's often talked about, but that’s mostly because it's not the most pleasant or commonly understood topic.
Sometimes, backflow preventer incidents do make headlines. For a prime example, consider Corpus Christi, Texas, where contaminated water affected residents over the course of multiple years. Many backflow devices hadn't been tested annually, and the potable water supply was severely compromised. A functioning backflow prevention assembly is necessary to ensure the water distribution system doesn't become contaminated.
Probably a higher percentage than you think, which is very bad news because a flooded vault increases the risk of worker electrocution, drowning or other confined space injuries. Repeatedly, water purveyors, cross connection control managers and backflow testers tell us that flooded vaults are a completely normal occurrence.
We at Safe-T-Cover don't have direct experience to give a specific number, but based on the regularity of flood events throughout the country and the risk flooded vaults pose to property and people alike, any flooded vault is one too many. For more insights on vault flooding, read this article from respected backflow tester and instructor Chris Mayhew.
It's great to be keeping the future of water system safety in mind. You'll pay three times over if you start with a vault, and then find out later that you have to retrofit to an above ground solution because the hazard level changed and now requires an RPZ, or reduced pressure zone assembly.
Safe-T-Cover sold over 50 above-ground enclosures to the state of North Carolina because they made revisions to the state code and had to update all state facilities’ double checks into RPZs at a tremendous cost. If they had simply started by putting double checks in enclosures, it would have simply been a matter of retrofitting the new device on the legacy pipe system, but because they began with vaults, they had to start over.
Even the smallest RPZ can discharge a dangerous amount of water at system pressure. The way most engineers work around these dangers is to install a floor drain or sink. However, this is almost always insufficient. Take the water flow rate of an RPZ and the drain's capacity into consideration to find out the needed drain size.
Without having to do the math, you can watch our video of one of these devices dumping water — just a small 3" device — and you'll know right away that the drain will not carry all the water from this backflow preventer. The water pressure is simply too much!
Watch our free Backflow Best Practices Recorded Webinar
Some fire systems are required to have RPZs. Namely, systems that carry fire retardant chemicals or even antifreeze within them. Such contaminants render the line a high hazard because they share the wastewater line.
There are two good reasons to stick with a DC assembly — double check valve assembly — for fire lines without these additives. First, head loss: an RPZ will deplete system pressure. In most cases, the loss is negligible, say, 4-9 pounds of pressure. But some cities are running on fumes when it comes to ambient pressure anyway; any loss is costly.
Second, remember that firefighting is about mitigating a clear and present risk of loss of life and property. What happens if the perfect storm scenario occurs just as firefighting efforts begin? Do you want an RPZ to dump all its available water when you need it most? A #1 check valve failure and a blocked relief valve will cause the water needed to fight the fire to be evacuated out the relief valve.
Regarding irrigation, every irrigation system, whether commercial or residential, should have an RPZ. Without a doubt, an irrigation system interacts with the highest concentration of contamination on a daily basis. For commercial users, the risk is with lawn chemicals. For a residential customer, it’s lawn chemicals and fecal waste from pets and wildlife. The EPA's Cross Connection Control Manual explicitly recommends RPZs for all irrigation lines. Many states address this risk today with RPZ requirements.
As you know, when RPZs dump, they dump a lot, so they really need to stay outside and in the civil engineer's domain. However, we know that if we're going to get the civil engineer to pick this matter up and handle it properly, standard details will help tremendously.
Providing standard details gives them guidance so that this relatively small part of their job can be done efficiently and is more likely to readily pass-through plan review processes. Yes, you could figure it out, but unless enough details are provided to ask an engineer who's never specified it before to start doing so, it’s unlikely they pick a new process up and start doing it a new way.
We suggest you contact us at Safe-T-Cover and say, "Here's my situation. I'd like to put this backflow assembly above ground. Do you have a standard detail that I could submit to my local authority and see it be approved?"
We've done so many of these standard details over the years, there's a strong likelihood that we already have a drawing that would support what you're trying to do. Then you just submit and see if any issues are raised at the local level, at plan review, and move forward from there.
Yes, Safe-T-Cover funds the development of standard details for placement in local districts and these districts at times will pay for the cost to have this done because they know they'll see value from the higher level of best practices in the area. This doesn't have to cost you anything.
By providing you a set of templates that are more than a set of blank or generic documents, we can demonstrate several cities full of results you can redline and say, "This won't work, but that would. I'd like to change that to this."
These are just some of the broad questions we received during that webinar. We didn't have time to address all of them live, so this page is meant to be a resource for design engineers and water purveyors wanting to follow best practices to better protect property and potable water systems.
To hear Randy Holland speak on these topics in greater detail, you can watch the backflow preventer installation webinar here.