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Pressure Vacuum Breaker Basics

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Pressure vacuum breaker
Aaron Stickley
A pressure vacuum breaker is an important component of irrigation systems. What a pressure vacuum breaker does is to provide protection against backflow or back siphoning of water. This irrigation component keeps non-potable water from inadvertently entering the water supply through outlets of the irrigation system.

Reasons To Use A Pressure Vacuum Breaker
There are several good reasons to install a pressure vacuum breaker as part of an irrigation system. The first reason is that most local building codes require the use of a backflow prevention device on all water systems. A pressure vacuum breaker is an affordable backflow option for use in residential irrigation systems. Contamination of the water supply can have wide ranging effects so prevention is very important. Since there is usually only one water system in the home for both drinking/household use and irrigation use there is always the risk contamination through cross-connections. Therefore, safety is another very important reason to use a pressure vacuum breaker in the home. When installing a new irrigation system check local codes for specific backflow prevention requirements and find out if a permit is required.

How A Pressure Vacuum Breaker Works
A pressure vacuum breaker consists of a check device or valve and an air inlet, usually a chamber vented to the atmosphere. The pressure vacuum breaker is installed close to the water source in the water flow before it goes into the sprinkler valves. It needs to be installed above the highest point in the system, usually the highest sprinkler head or the highest slope in the yard. The check valve is designed to allow water through and keep the air inlet closed during normal conditions. When the air pressure is greater than the water pressure the vented chamber opens and closes the check valve preventing backflow of water.

How To Maintain A Pressure Vacuum Breaker
Since the pressure vacuum breaker is such an important part of an irrigation system it is important to ensure it is working properly. If you are concerned about a pressure vacuum breaker a test can be performed. Local building codes determine whether a homeowner is allowed to perform the test or whether a professional must be called in.

Regular maintenance for a pressure vacuum breaker is minimal. The internal components should be replaced after about five years or as specified by the manufacturer. Another way to ensure that a pressure vacuum breaker continues to work properly is by winterizing the whole sprinkler system. Winterizing the sprinkler system to prevent freezing is required since pressure vacuum breakers are subject to damage from freezing. Local building codes determine whether an inspection is required when a sprinkler system is started up after it was shut down for the winter.

How To Repair A Pressure Vacuum Breaker
The internal components of a pressure vacuum breaker can become damaged by freezing and by normal use pressure over time. A clear sign that something is not working properly is leaking from under the bell or bonnet assembly of the valve. Repair kits are available from the manufacturer that are specific to each pressure vacuum breaker model. The repair consists of turning off the inlet and outlet ball valves, then removing the bonnet assembly. Since the repair parts are installed in the reverse order it is a good idea to keep the components well organized as they are removed. The repair parts are then installed and the water supply is turned on (inlet water supply valve first). Once again local building codes determine if a homeowner is allowed to repair the backflow device or not. Most often, even when a homeowner is permitted to repair the backflow device inspection of some sort is required.

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