We install Excess Flow Valves (EFV’s) on service lines to limit the flow of gas in the event the line is broken or is severely damaged. This is most often associated with excavation or vehicle impact with the meter assembly. If you have an existing EFV, it is typically installed either at the service line connection to the gas main or at the customer’s property line.
How do Excess Flow Valves work?
The EFV and gas meter are sized based on the total anticipated load of the existing gas appliances. When gas appliances are turned on, the flow is not enough to push the valve shut. However, if the service line pressure drops suddenly due to gas escaping from the damaged pipe, there is enough pressure differential to close the valve allowing only a slight bleed-by. Bleed-by, or bypass of gas, is achieved with a small notch in the valve seat. Once the damage downstream is corrected, the bleed-by flow of gas allows for pressure equalization of the upstream and downstream sides of the valve, allowing the valve to reset into the open position.
How will an Excess Flow Valve affect my gas service?
An EFV should not affect the delivery of your gas service as long as the service line is intact. If gas appliances are added, 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. Contact gasinfo@mesaaz.gov to check if your meter or EFV can handle the additional load. If it is determined the EFV needs to be upgraded to meet additional load, it will be replaced at the customer’s expense.
It is important to note that an EFV does not shut off the flow of gas completely. A very small amount of gas may bleed by. The gas may not be escaping under full pressure, but there will typically be enough gas to provide a gas odor, indicating there is a problem. Because an EFV restricts the flow of gas, it reduces the potential for explosions, fires, and personal injury. To report a damaged service line or if you smell gas in or outside your home call 480-644-4277 or 911.
Does my gas service have an EFV? How do I request an Excess Flow Valve?
We have installed EFVs on new and replaced residential gas services since January 2008. In April 2017, Mesa expanded installation to include multi-family residences and single, small commercial services not exceeding 1,000 SCFH (Standard Cubic Feet per Hour). A visual indication of the presence of an EFV is the installation of a washer on the meter riser. 
To check if your gas service has an EFV or to learn about the requirements to have one installed, contact us at gasinfo@mesaaz.gov. As a customer, you have the right to request an EFV if your service does not have one, and the gas service does not exceed 1,000 SCFH or those exceptions identified in 49 CFR 192.383(c).
How much does it cost to install an Excess Flow Valve?
The cost to the customer to install an EFV varies depending on site conditions, most often associated with replacement of concrete or pavement and if traffic control is necessary. In 2021, fees ranged from approximately $1,000 to $5,200 depending on the scope of work. The installation of an EFV involves excavation of the pipeline and may temporarily interrupt gas service. We will be responsible for the future costs to maintain or replace a malfunctioning EFV.
How do I get more information about EFVs?
Contact us at gasinfo@mesaaz.gov to check if your service has an EFV. Please include your full name, telephone number, preferred email address and the property address you are researching.