The Lawn & Sprinkler Guys conducts hundreds of backflow preventer inspections each year. This is one of the most important services we offer because there is a safety aspect involved.
Backflow prevention devices protect the drinking water system from contamination due to backflow of non-potable (contaminated) water into the potable (fit for drinking) water supply. Backflow is of two types: back-siphonage and back-pressure.
Any drop in pressure in the main city water line can result in back-siphonage backflow of fertilizers, pesticides, manures and other contaminants through sprinkler heads and the irrigation piping system into the potable water supply. This same contamination may occur through a hose-attached sprinkler, spray nozzle or pesticide sprayer. This presents a serious threat to public health. This drop in pressure can result from a break in the line or by lowered mainline pressure due to high water withdrawal, as may occur during fire fighting operations.
Improper installation of a lawn sprinkler pump or injector system may force contaminants back into the potable water supply. In this case, the pressure exerted by the pump is greater than the pressure in the potable water system. This is known as back-pressure backflow.
If properly installed, an approved backflow prevention device will prevent back-siphonage and/or back-pressure backflow. Not all devices are designed to handle both types of backflow.
Backflow prevention devices are designed for installation on sprinkler systems connected to potable (drinking) water supplies only. Sprinkler systems only connected to irrigation water (ditch systems) do not require backflow protection.
Permits normally are required for systems that require backflow prevention devices prior to the installation of a sprinkler system. The installation design, to include the type and placement of backflow prevention devices will be approved during the permit review process. Permits are available from city/county building departments.
The Lawn & Sprinkler Guys will inspect your backflow preventer device annually and make sure it is safe, is in good condition, and is approved by the necessary required municipality.
To read more about backflow preventer inspections and devices, check out this Wikipedia page.