Excess Flow Valves (EFVs)

Excess Flow Valves (EFVs) are installed on single family residential service lines. 

What is an Excess Flow Valve (EFVs)?

An EFV is a mechanical safety device installed in conjunction with 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 (EFVs) work?

A spring pushes a valve open against the oncoming gas flow.  Sensing a change in pressure, the spring forces valve closed, minimizing the flow of gas.  EFVs 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 gas pressure continues pushing on the valve, keeping the valve closed until the correct pressure is restored by the City.  When lines are repaired and service is restored, the valve automatically resets itself.

How will an Excess Flow Valve (EFV) affect my gas service?

Your EFV may affect your gas service if the service line is damaged.  A small puncture of the service line typically won't trip the EFV, 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 to indicate a gas odor.  To report a damaged service line or if you smell gas in or outside of your home, call 480-644-4277 (GASS).

The EFV 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 Mesa's Development and Sustainability Department at 480-644-4273 (select option 1 for English, then select option 1, Building Permits/Right of ways) to check if your meter can handle the additional load.  If you need a larger meter, we will schedule an appointment  and install the appropriate meter during regular business hours at no additional charge.  If it is determined the EFV also needs to be upgraded, it will also be replaced. 

Excess Flow Valve Flow Chart

Remember, prior to any excavation project, call Arizona 811
(dial 811) to have your underground utilities located.



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PO Box 1466
Mesa, AZ 85211

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Frank McRae, Director