Backflow preventers are required by law because they prevent contaminants from getting into a drinkable water supply. There are several types of backflow preventers to choose from. The primary factor to keep in mind is the potential for cross-contamination between the gases and the water supply. If it’s determined that cross-contamination is incredibly likely, that’ll influence which backflow preventer you choose. This article will help readers understand the different types of backflow preventers so that the water supply remains safe for consumption.
Atmospheric Vacuum Breaker
One type of backflow preventer is an atmospheric vacuum breaker (AVB). This device has a kink in it similar to the shape of an elbow, and there’s a valve inside that stops the water from flowing backward. This simple design makes AVBs easy to install, repair, and maintain. Before discussing AVBs any further, it’s vital to go over the parts within the devices. They are the following:
- Inlet shutoff valve (at the bottom)
- A single valve body
- A check valve
- Two test clocks
- Outlet shutoff valve
Essentially, the flow of water causes the inlet valve to open and shut at the bottom. At the same time, a check valve is opened to allow air to come in and create the pressurized effect it’s known for. In order for the water to flow and stop as needed, nothing should obstruct it.
Pressure Vacuum Breaker
A PVB assembly has an air inlet valve that opens when the internal pressure system is higher than the external pressure system. PVBs are typically installed vertically about a foot above the highest downstream in the plumbing system. The primary disadvantage of PVBs systems is that they typically don’t protect against high backpressure. PVBs are mostly suited for backsiphonage as opposed to backpressure.
What’s the Difference Between Backsiphonage and Backpressure?
Backpressure occurs when there is a mixture of water and air. This mixture goes into a set of chemicals. When too much air is in the pressurized mixture, the leftovers flow backward. Backsiphonage is when an unexpected sprout of water causes a drop in pressure.
Spill-Resistant Vacuum Breakers
AVBs and PVBs often leak water. Consumers that want to avoid this can get a spill-resistant vacuum breaker. SRVBs are constructed similarly to AVBs and PVBs, except an additional part seals in water when the air inlet is turned on. Like AVBs and PVBs, SRVBs protect against backsiphonage, but not backpressure.
Double-Check Valve Assembly
A double-check valve assembly typically lies underground. DCVAs consist of the following:
- An inlet shutoff valve
- Valve body with two spring-loaded independently operated check valves
- Four test valves
- Outlet shutoff valves
A DCVA runs parallel to the piping system. It can be installed horizontally or vertically. DCVAs don’t need to be installed a foot above the downstream in the piping system, either. Instead, some room has to be left for maintenance. These check valve assemblies protect against backsiphonage and backpressure. However, they should only be used for low-pressure situations and not, for example, installed in a fire protection system.
Reduced Pressure Principle Backflow Assembly
This type of backflow preventer is one of the safest on the market today. It’s also one of the most complex ones to install and maintain. RPs consist of:
- Inlet shutoff valve
- A pressure-differential release valve that separates two loaded spring valves
- Four test valves
- Outlet shutoff valve
There is also a mechanical relief valve that maintains a low-pressure zone between the check valves. RPs are incredibly flexible and can be installed underground, aboveground, or horizontally or vertically. However, installing things vertically may take a little more brainpower. RPs can also protect against backsiphonage and backpressure and can withstand high or low-level scenarios.
How Do You Choose the Right Backflow Preventer?
We have gone into detail about what each backflow preventer does and what it should be used for. So, how do you choose the right backflow preventer? Here are a few factors to keep in mind:
- Location: AVBs and PVBs should be used in low-level environments (such as a household.) This is because they can protect against backsiphonage but not backflow.
- Application: Whether you are installing a backflow preventer in an irrigation system, a traditional plumbing application or fire protection, there are different types for each. :
- Complexity: The final factor you should keep in mind when choosing a backflow preventer is its complexity. How challenging will it be to install and maintain the backflow preventer? Typically, PVBs and SRVBs are the easiest to take care of. RPs are incredibly difficult to maintain because there are more parts that could get damaged.
This article has helped people struggling with understanding the different types of backflow preventers. Some backflow preventers are more suited for high-level situations. RPs, for example, can withstand intense situations such as a fire. On the other hand, AVBs and PVBs are better suited for household plumbing where issues might not be as severe.
Backflow Direct can help with backflow preventer assembly. Our team knows which device is meant for which situation. We also offer a variety of different sizes so that you can rest assured you get the right device for the job. Our team will also keep in mind important factors so you don’t end up having to replace the tool in the future. We will stay within your budget, help determine where the preventer should be located, and the complexity of the part. Whether you need a backflow preventer for a household or a fire protection system, Backflow Direct has your back. We’ll work with you as a team, rather than just take over the job entirely. Trust us; we know our stuff.