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What is an irrigation backflow preventer used for?

October 27, 2015
Brad Bippus

There are two extremely important reasons that your irrigation backflow prevented is used for on your irrigation system. One of the reasons is to protect your potable water supply against back pressure.   The second reason is to protect your potable water supply against back siphonage.  Your backflow preventer needs to be installed before all of your irrigation components.

Your backflow device is THE key component in protecting your water supply for your family and you.  The chemicals used on your lawn and other outdoor contaminants cannot get back into your drinking water with a properly functioning back flow.  These harmful contaminants can get into your sprinkler lines through drip emitters, through the sprinkler heads, when you repair a leak in one of your pipes,  or when you repair any other part of your sprinkler system and get dirt into it.

Back pressure is what happens when the pressure is greater on the outflow side of the device and lower on the inflow side of the device. This can happen from a variety of different causes.  It might happen if there is some work being done on some plumbing in the house. The water in the pipes is draining from the work in the house and it loses its pressure but the irrigation system maybe fully pressurized. Another situation where this may occur is when the neighborhood supplied water is being worked on and the pressure supplied to the house drops and causes the irrigation system pressure to be higher than  incoming house pressure.

Wilkins 720A Pressure Vacuum Breaker

Back siphonage is another issue that the backflow device protects against. This is similar to the back pressure issue.  It can be best explained by using the straw analogy.  Water is being sucked back through the pipes because of the pressure differential.

Back siphonage generally occurs when there is a hose attached to a hose bib on the house. The end of the hose could be in a contaminated pool of water while someone in the kitchen is filling a pitcher of water.   This creates a pressure differential and water could be sucked back into the house through the hose.

And remember, a backflow device is required by Federal plumbing code to be installed on an irrigation system. It not only protects your home’s drinking water, it also protects the communities water supply from contamination.

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We install high quality, long lasting sprinkler systems for all your planting needs.  Including gardens, xeriscape, lawn, trees and bushes.

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