Why the need for Backflow Prevention Assembly Installation?

Atlas Backflow provides Backflow Prevention Assembly Installation Services.

You’ve received a letter from the water company. It states that a backflow prevention assembly must be installed at the service connection. The two biggest questions that are presented to us are: What is a backflow? Why do we need it?

The answers are fairly straight forward.

What is a backflow prevention assembly?

Let us explain in the easiest of terms. A backflow prevention assembly is a water valve that allows water to FLOW in one direction and keeps that water from ever BACKing up. Kind of like walking through a bus turnstile. You walked through the turnstile. What happens when you try and walk back through it in the opposite direction? You can’t. It only allows you to enter one way. Unless of course to jump over it. “Backflow Prevention” basically means NO BACK FLOW. No going back. Chances are, you’ve seen these backflows everywhere, but haven’t given any thought as to what they are and what purpose they serve. See photos below. Look familiar?


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So, why the need for a backflow installation on your property? Again, the answer is pretty straight forward. Walk out to the front of your property. Take a look at all of the other buildings in the area. You can assume that every building has water being supplied to it, right? The water that’s being supplied their building is the same water that’s being supplied to yours. Now, where is that water coming from?

Answer: The water company that you buy the water from.

Go on…

The Water company sells and distributes water throughout their customer base. Distribution is done through web a underground water mains. If your still standing outside, look up and down the street. Under all the asphalt and concrete lies a fairly large water pipe. This pipe travels up and down your street. It then bends and tee’s off to travel up and down other streets, boulevards, roads and avenues. Off of this water main, are smaller waterlines that branch out to supply water to individual properties. Like the blood traveling throughout your body, you have bigger arteries (water mains) and they branch out into smaller veins (waterlines) that supply blood to your legs, arms, fingers and toes.

Safe Drinking Water

One of the most important duties that the water company has to account for, is the maintenance and delivery of safe drinking water to its customers. Water is used for many, many purposes, and not just for washing your hands or flushing the toilet. Some commercial and industrial processes use hazardous materials in their facilities. Click this link to see a list of examples. https://www.bonnersprings.org/888/Why-Do-I-Need-a-Backflow-Prevention-Devi

Ok, but even if any of this applies to my building, how would any contaminants get into the drinking water?

Ok, let’s take this home!  A backflow preventer keeps a backflow event from occuring. A backflow event can occur because of backsiphonage or backpressure. Backsiphonage happens when the upstream water pressure in a piping system drops to a subatmospheric pressure. In simple terms, think of when a fire hydrant get hit by a car. The water blowing out of that hydrant, in most cases is from the same water main that supplies the water to you building. If this were to happen, you would like notice either extremely low or no water pressure in you building. That’s because all of your water was sucked out of your buildings waterline and back into the districts water main. Whatever was in your waterline, also went along for the ride. That includes any of the hazardous materials, resulting in the contamination or polluting of the public drinking water. Yuck.


Backpressure is when the pressure on the downstream side of a piping system is greater than the pressure on the upstream side – common causes and sources of backpressure include pumps, elevated piping, thermal expansion, and pressurized containers. Just know, that like backsiphonage, backpressure can also introduce hazardous materials into the public drinking water through the reversal of water flow.

To recap…

Backflow is the reverse flow of detrimental and dangerous material into water mains. When there are connections between publics water supply and sources of possible contamination it is potentially dangerous. Connections between drinking water lines and commercial and industrial plumbing systems can be deadly. These connections are called cross connections. The Water Department is responsible for ensuring the water is safe for everyone to drink. It is the water districts responsibility to keep the water main (main artery) safe from dangerous pollutants and contaminants. One of the ways in which the water district can accomplish this is by requiring that it’s customers have a water backflow prevention assembly installed.