Excess Flow Valves

On January 1, 2008 the City of Mesa began installing Excess Flow Valves on new service lines for single family residential homes.  Excess Flow Valves may also be installed if a service line is in need of maintenance or repair on a single family residential home.

What is an Excess Flow Valve (EFV's)?

An Excess Flow Valve is a mechanical safety device installed inside the City's gas service line.  In the event of damage to the City's gas service line between the street and your meter, the EFV will "trip", minimizing the flow of gas through the service line and reducing the amount of gas vented to the atmosphere.

 How do Excess Flow Valves work?

A spring pushes a valve open against the oncoming gas flow.  As more and more gas flows by the valve, the spring can no longer overcome the force of the gas and the valve seals shut, stopping the flow of gas.  Excess Flow Valves are designed so that when you turn on your gas appliances, the flow isn’t enough to push the valve shut, however, if the line is damaged, there is enough flow to push the valve shut.  After the EFV trips, the high pressure gas continues pushing on the valve, keeping the valve closed until pressure is restored on the downstream side of the valve.  When lines are repaired and service is restored, the valve automatically resets itself.

How will an Excess Flow Valve affect my gas service?

The Excess Flow Valve and gas meter installed at your house was sized based on the homes gas appliance load.  If you add additional gas appliances such as a barbeque, pool/spa heater, or fire pit, the additional gas appliances may make your total gas demand too high for your current gas meter and may affect the operation of your EFV. 

Prior to installing additional gas appliances, contact the City of Mesa’s Building Safety Division at 480-644-4273 to check if your meter can handle the additional load.  In the case that your meter needs to be upgraded to a larger model, we will schedule an appointment with you to set a larger meter at no charge to you.  If it is determined the Excess Flow Valve needs to be upgraded, we will replace it at no charge to you. 

Your EFV will also affect your gas service if the service line is damaged.  A small puncture of the service line typically won’t trip the EFV, but rather it requires significant damage to activate.  There will not be any blowing gas to identify that a line has been damaged, but there will typically be enough gas that you will be able to smell the leak.  To report a damaged service line or if you smell gas in or outside of your home, call 480-644-4277 (GASS). 

Remember, prior to any excavation project, call the Arizona Blue Stake Center at 811 to have your underground utilities located.