What is a backflow device?
Backflow devices are simply components of plumbing systems installed to prevent contaminated or polluted water from backflowing into the fresh water supply. This can be the result of backpressure, where the pressure on the supply side (fresh water coming into the building or irrigation system) is exceeded by something causing greater pressure (a fertilizer pump, a big tank on top of a tower or tall building, etc.). If the pressure on the supply side drops below the pressure on the demand side, the potentially bad water can be forced back into the fresh water supply. When this happens, many people can get sick or die as a result of being exposed to the contaminated or polluted water. If a backflow incident should occur resulting in the contamination of the public water supply, the responsible owner or occupant could be held liable for damages. With backflow devices installed, the water cannot flow back, as it is stopped by a check valve (or two) that only allows water to travel in one direction.
Typical commercial buildings have the three most common types of devices. While you may not realize it, you see them all the time The most easily recognized backflow device is called a DCDA, or double check detector assembly. Usually painted bright red, these are large (usually at least 6” in diameter) pipes with rising-stem shutoff valves located near the curb. While some are hidden behind hedges or walls, they're hard to miss.
Fig. 1– Double Check Detector Assembly (DCDA) backflow prevention device
These valves are specifically for the fire sprinkler systems inside buildings or covered walkways. This valve prevents the static water sitting in the sprinkler system from backflowing in the water supply, contaminating it with bad water. If there is a fire, the fire deparment will help boost the pressure of the sprinklers by attaching a hose from a pump engine to the demand side of this valve, adding additional water to the sprinkler output. This pressure is also applied to the back side of the check valves in the backflow device, and the DCDA prevents this water from backflowing into the water supply.
The most common use of backflow devices is to protect the fresh water supply coming into the building. The valve shown below is the most typical, called an RP or RPP. This stands for Reduced Pressure Principle, and descripes the way it works. It performs similarly to a double check, with an additional feature; it also has a relief valve. This additional valve insures that should an internal check valve fail, the contaminated or polluted water can't backflow into the water supply as the relief valve will open and vent the water onto the ground. If you notice a large stream of water venting from your valve, call a backflow tester right away.
Fig. 2 – Reduced Pressure Principle (RPP) backflow prevention device
The third type of backflow prevention device typically found at most sites is the Vacuum Breaker. These come in three types: the Pressure Vacuum Breaker (PVB), Atmospheric Vacuum Breaker (AVB), or Spillresistant Vacuum Breaker (SVP). Their purpose and application is dependent on the site requirements. They're tested to insure their internal check valves are in working order, and serve the same purposes as the valves listed above.
Why do backflow valves need to be tested?
Typically, your water purveyor requires that the owner of the valves have them tested annually by certified testers. As they are mechanical devices and have internal moving parts, they sometimes fail and must be repaired immediately to prevent a backflow condition.
Once you receive your test notice from the water company, you typically have 30 days to get them tested by a certified tester. Here in Orange County, California, the testers must pass an extensive classroom and hands-on training curriculum, followed by a practical exam with the Orange County Health Care Agency/Environmental Health Department. Upon completetion of the exam, the testers are certified and assigned a certified tester number.
If the tester determines that your valve fails, you'll be notified that it needs to be repaired or replaced immediately. While some testers only test valves, others are trained in their repair or replacement as well.
Backflow Device Theft on the Rise
The rising cost of building materials, specifically copper, brass, and bronze, has given rise to a new challenge for law enforcement. Recently, thieves have discovered that backflow devices are a quick source of cash in the form of scrap metal. With each valve bringing about $250 in scrap value, brazen thieves have been taking them at any time of day or night, leaving the owners without water, or worse with water damage caused by the unrestricted flow.
Scrap dealers have been notified by law enforcement to be on the lookout for these valves. Unfortunately, hundreds of valves are stolen in southern California each day. Each valve is serialized, however this does not deter some disreputable scrapdealers who will accept them.
There are many ways to prevent or minimize the damage these thieves can cause. Let us advise you of many of the ways our customers have made small, inexpensive changes and helped prevent their theft.
For example, while the cage below can be easily defeated by a determined thief, most will simply move on down the street to the next one that is unprotected. The concrete foundation, the cage, and the labor to install it can add up to be a substantial amount, especially if you have many valves to protect. On the other hand, replacing just three backflow devices can cost as much as $3,000 to $6,000 for 2” devices (the most common target).
Once a thief has successfully taken a few devices from one property, they have a habit of coming back to take the new replacements as well.
