MrBobDobalina

While that is probably true for most places, Baton Rouge Water Company employees tasked with the install are usually about the cheapest and most under qualified members of society you could imagine to be trusted with the sanitation/ preservation of a healthy water supply. The dual checks they (sometimes) use are pocket sized and are quite prone to failure. They also are unable to be tested or repaired. That difference separates BFPs (which are referred to as assemblies) from Dual checks which are classified as devices and do not provide proper prevention for backflow. Dual checks are buried underground while BFP's live above ground with us. They can't do their job without exposure to atmospheric pressure.

It is important to note that there is a BFP assembly that is called a DCV or Double Check Valve that is most commonly used on fire suppression systems to prevent rusty sprinkler water from ending up in your coffee pot at work.

Dual check, roughly the same size as a tube of chapstick:


Double Check Valve, range from about 18" long up to 4 feet long in commercial buildings and can weigh upwards of 200 pounds.




I promise I'm not on the bad guys' side. I don't care if you install them or not. But they absolutely serve a purpose and do it very well (when reasonably maintained.) They're required on any new commercial building for that reason.

I 100% disagree with retroactively making people install them and foot the bill entirely like what has happened here over the past year. We pay taxes and pay the water company enough money that this could've been rolled out much more smoothly over a longer time frame and proper compensation should've been paid to anyone that was made to install them retroactively. The end user sees no benefit from installing one, only the water supply system as a whole. :usa:

Full disclosure I am not an engineer/physicist just a plain jane degree and a good bit of experience with backflows. It can happen 2 different ways, back pressure and back siphonage.

When your sprinkler system is not in use, it is at static city pressure. A BFP isolates the drinking water from the sprinkler water like a check valve (that's all they really are is over built, enormous check valves), it will stay at the same PSI until you turn on your sprinklers. Without a BFP, the two systems are "cross-connected" and technically water can flow back and forth from the city piping, into your residential piping, back into city piping indefinitely.

In the situation above with no BFP installed, the water in the sprinkler system has no way to exit the system, sprinklers aren't running. The city sends you water at let us say 65 PSI, it only achieves this maximum pressure at 3 in the morning when very low demand is on the water supply system. When you, your neighbors, and the apartment complex down the street from you use water (peak demand hours), the city's water pressure drops to a lower PSI (say 55 psi) than the sprinkler system was at when it rested overnight at low demand hours. This water in the sprinkler system will flow backwards due to the pressure differential until it catches air and "burps" itself, or until the pressures equalize. Anything near those sprinkler heads (think fertilizers, pesticides, pet fecal matter) has the potential to be drawn into the piping and sent backwards into the city supply. This gets magnified enormously if the city water supply system goes offline (for repairs or a water main blows out) or experiences significant drops in pressure during peak demand.

You can get in the weeds with backflow and find examples that blame it on the venturi effect from pumps going off line or breakages allowing suction to draw water into the piping system. I like to paint a simpler picture. Water in pipes (especially under pressure) can behave very different from how you might expect under a particular set of circumstances, these are only installed to remove the risk from those special circumstances.

TLDR BFPs act as check valves that can introduce air into the piping system to relieve back pressure or back siphonage from the side that they were installed to protect.

The purpose is for when your pressurized water system becomes depressurized. Whether its a break in the line or the city shut your supply off to do a repair etc. etc. I'm not harping on them, I think they serve a good purpose that benefits the water supply system as a whole, but I think its insane what they tried to pull last year making every business (in EBR) install one by a certain date.

At a minimum the city should've subsidized 1/2 the cost for everyone as the business owners receive no benefit from protecting the water supply and still had to foot the entire bill.

The reason they are important on sprinkler systems is because the heads are below grade when not running and dirt/debris from the yard or fertilizers or herbicides can easily travel backwards into the municipal water supply without one. If the sprinklers aren't isolated by a backflow, anytime water is used there is potential for the water to be drawn out of the sprinkler lines and into the lines that serve the city or your house.

Its a 1/100,000 chance that someone leaves their hose in a bucket of herbicide and walks away at the same time Bubba cuts into the water main but you spread that out over an entire city or state and you have instances of morgue "fluids" backflowing into water supply or 2-4-D contaminating an entire parishes water supply because the farmer left his sprayer filing while he went to get diesel. You will probably never be the one to commit the frickup, but having BFP's installed everywhere acts as a fail safe for the lowest common denominator.

Dang I'm supposed to sell the news but I couldn't resist grabbing a few more shares

Vermicelli Noodles.

It doesn't make sense until you try it.

Are you looking for a frost proof hose bibb or a faucet for a sink?

Windy

Dammit my baw somebody already started this thread just for you and you missed it!!

I want to add more here but I know when I do I'll give it all back tomorrow.