The pressure vacuum breaker is one of the most important components in your lawn and landscape sprinkler system. If it fails, your system can inadvertently siphon chemicals, bacteria and other harmful agents into your home's drinking water supply. Below is more information on backflow prevention and pressure vacuum breakers and a few simple maintenance tips:
A brief introduction to backflow prevention
In every instance when your home's water supply is connected to an underground irrigation system, a backflow prevention device is necessary; in some locales, these devices are even required by law, though their use should not be considered optional regardless of legality.
In ordinary circumstances, the water entering your sprinkler pipes and heads is under pressure; this pressure pushes outward, and no contaminants from your lawn and soil can enter into the irrigation plumbing. However, if the pressure disappears or lessens significantly, such as during a general water main shutoff or line break, the newly created vacuum in the water supply lines in your home will begin to exert a strong suction on the sprinkler system. Much in the same way as you suck on a straw, the vacuum will "pull" contaminants from the soil into your water lines. This can lead to problems ranging all the way from minor taste issues to serious illness or poisoning. The only safe way to prevent this problem is by installing a backflow prevention device between the underground components and the water supply.
What your pressure vacuum breaker does
There are many types of backflow prevention devices, but pressure vacuum breakers are the most commonly used design type in irrigation systems. They are low cost, reliable and easily maintained by homeowners. While you don't need to understand all of the intricate working details, it is helpful to know that pressure vacuum breakers work by closing check valves in response to a loss of water pressure. The vacuum serves as the stimulus that forces the valve closed, and backflows are effectively eliminated as a result. However, if contaminants clog the inner components of the valve, then it may fail to close properly, resulting in leaks or backflow.
How to maintain a pressure vacuum breaker
As a homeowner, there are several things you can do to maintain your pressure vacuum breaker and help ensure it provides long-lasting service. Here is what you can do:
Ensure pressure vacuum breaker remains at proper operating height - In order for your pressure vacuum breaker to function, it must remain higher than your tallest sprinkler head or line elevation. That means if you have added irrigation components recently, such as on a sloped area of your lawn or garden, then you will need to compare heights to ensure your system is still operational. "Short" pressure vacuum breakers will need to be elevated by a qualified professional who will insert additional pipe lengths.
Watch for leaks from bonnet - A tell-tale sign your pressure vacuum breaker has failed is water leakage from the area beneath the device's bonnet, the topmost component that resembles a bell. No water should emerge from this area, and a service call for repair or replacement of the unit will be needed if you find a leak.
Keep your pressure vacuum breaker clean - Since the pressure vacuum breaker in your home's irrigation system may be found in an out-of-the-way location in your yard or garden, it may be easy to neglect it or the surrounding area. However, be sure to keep grass and weeds away from the unit to avoid problems vegetation overgrowth. This will prevent possible corrosion as well as keep vines or stems from growing into or around components. In addition, if your pressure vacuum breaker becomes dirty or covered with mold, wash it periodically with a solution of water and bleach to keep it clean.
- Get the device tested if necessary - If you are concerned about your pressure vacuum breaker's operation or believe it may be time for a replacement, ask an irrigation specialist to perform a test of the device. They can diagnose potential problems and proceed with repair or replacement.