Fisher 83895 Water Station with 14" Pedestal Glass Filler - 2.2 GPM

Hi, this is Jeff. Today, I'd like to talk to you about backflow prevention, but before we begin, please note that it's important for you to check with your local municipality to find out their requirements regarding backflow prevention in your area. Backflow is the unintended reversal of the normal flow of water in a plumbing system. It's caused by one of two conditions: back siphonage and back pressure. Back siphonage occurs when the normal pressure in the system turns negative, causing a reversal of the normal flow of water in the system. Back pressure, on the other hand, is when the pressure on the outlet side of the fixture is greater, causing the water to reverse itself in the water system.

Fisher offers four general types of backflow prevention. We use an air gap, we use an atmospheric vacuum breaker, a dual check valve backflow preventer, and an anti-spill pressure style vacuum breaker. Each has its own unique application. Air gap is the distance between where the water comes out of the fixture and the flood rim of the sink. You need to maintain a minimum of 2" air gap. The dual inline check valve backflow preventer is used whenever you have a flexible air gap, such as on a pre-rinse where the outlet of the device could well be below the flood rim of the sink. Atmospheric vacuum breakers commonly found on kettle fillers and service faucets are designed to prevent back siphonage. The caution is that you are not allowed to have any shut-off valves downstream of the atmospheric vacuum breaker. Anti-spill pressure style vacuum breakers are commonly found on hose reel units. They protect against back siphonage, back pressure, and it's important to note that you can have valving on the inlet side of this and the outlet side of it. And they are not to be installed above ceiling tiles in the wall, it must be accessible for inspection. Backflow prevention can be quite complex, however, in the Fisher catalog we offer many kits and components to make the process quite simple. Be sure and check your local codes. Thanks for watching.