There are two main ways in which backflow may be caused: backpressure and back-siphonage. First we will talk about back pressure, backpressure occurs when a potable water system is connected to another water system operating at a higher pressure. Backpressure can be caused by auxiliary pumps or boilers within the non-potable water system. Backpressure can sometimes even be caused by elevation differences. The second cause we will talk about is backsiphonage, backsiphonage is caused by a reduced or negative pressure in the potable water supply line. This reduced pressure could be caused by various situations including: an open hydrant, water system maintenance, or a water main break.
It is extremely important to use the correct backflow prevention assembly device to combat each potential backflow situation. There are several factors that will determine which type of backflow prevention assembly device should be used. To determine which device is best for your property, it is suggested that you contact a backflow tester and receive professional advice.
The most important factor in deciding what backflow repair needs to be performed on your system is the city code of the city your property is in. If you try to do the repairs without a backflow expert you may make the mistake of guessing which product is the correct product to use for a specific application, and you may guess wrong. An example of this may be you have a property in two different cities, the backflow valve you use in one city may be different from the one that is required in a different city. If this happens you would have to remove the valve and replace it, costing extra. You may also receive a fee from the city for not installing the correct device. This can all be prevented by having a backflow prevention test performed by a certified backflow tester.