Excess Flow Valves

In keeping with a new federal regulation, Eversource wants you to know about your right to request the installation of an Excess Flow Valve (EFV) on your existing natural gas service line.

diagram of excess flow valveAn EFV is a mechanical safety device installed in a natural gas service line between the natural gas main and the natural gas meter. EFVs minimize or stop the flow of natural gas in the event of a service line break. EFVs do not stop the flow of gas for any leaks or faulty equipment on the customer’s side of the gas meter.

If you or an excavator accidentally digs up the natural gas service line and severs the line, the EFV will automatically minimize or stop the flow of natural gas. For your safety, always call Dig Safe at 811 whenever you or a contractor plan to dig near your service line.

Many customers already have an EFV installed in their existing natural gas service line. However, EFVs will not work properly on all natural gas services, which means not all customers qualify for an EFV. Eversource can determine if an EFV is right for your property based on the amount of gas it requires, the pressure of the natural gas system and other technical factors (see below).

Cost & Installation

Current Massachusetts regulations state that each customer must pay the equipment and installation costs for an EFV. Costs range between $2,000 and $4,000, depending on your specific location. 

Eversource, along with other Massachusetts gas utilities, has advocated that EFV costs be shared across all customers through gas distribution rates. Once the Massachusetts Department of Public Utilities (DPU) makes a determination regarding that request, Eversource will begin scheduling customer-requested EFV installations consistent with the DPU decision.

If you decide you want an EFV, Eversource will work with you to set up a mutually agreeable installation date. Installation requires Dig Safe notification and excavation where the existing gas service line connects to the gas distribution main.

Gas service must be interrupted in order for Eversource to safely complete the installation. We will then relight all gas appliances. 

Request An EFV

Eversource is pleased to answer any questions you have about installing an EFV at your property. If you are interested in an EFV or are wondering if you currently have an EFV on your natural gas service, please contact us at 844-417-0252 or


Technical Factors Preventing the Installation of an EFV

  • The service line does not operate at a pressure of 10 psig or greater throughout the year;

  • Eversource has prior experience with contaminants in the gas stream that could interfere with the EFV’s operation or cause loss of service;

  • There is potential for interference with necessary system operation or maintenance activities;

  • An EFV meeting the performance standards set forth in federal regulations is not commercially available to the company.