Excess Flow Valves

An Excess Flow Valve (EFV) is a mechanical shut-off devices that can be installed in the gas pipe running from the gas main to the gas meter at your property (the “service line”). It is designed to shut off the flow of natural gas automatically if the service line breaks, for example, by an excavation accident. Stopping the flow of gas from a broken service line significantly reduces the risk of natural gas fire, explosion, personal injury and/or property damage. EFVs are not designed to close if a leak occurs beyond the gas meter (on house piping or appliances). EFVs also may not close if the leak on the service line is small.

Excess Flow Valve

New and Replacement Natural Gas Service Lines

As part of our commitment to safety, and in compliance with federal safety regulations, Middle Tennessee Natural Gas Utility District (MTNG) installs excess flow valves on any new or replacement residential natural gas service line, as well as on certain commercial service lines.

Existing Natural Gas Service Lines

If you have a natural gas service line which was installed prior to the development of EFVs, you may request that MTNG install an excess flow valve on the gas line to your property. If you notify us that you want an EFV, we will contact you to set up a mutually agreeable date when we will install an EFV on your service line. There will be a charge for this service: $200.00 for an EFV installed on a ¾” service line, or the actual cost of installation for an EFV installed on a service line greater than ¾” in diameter, up to and including a 2” diameter service line. EFV installations on service lines larger than 2” diameter will be evaluated on a case-by-case basis.

Changes in Natural Gas Usage

If you add additional gas appliances, for example, a pool heater, emergency generator, etc., the additional gas flow may cause the EFV to close. Please notify your closest MTNGUD Office before adding significant new gas load to ensure we don’t need to upgrade your EFV.

Maintenance and Replacement

If it becomes necessary to maintain or replace the EFV on your service line we will maintain or replace the EFV at no charge to you. EFV replacement may be necessary if you add additional gas appliances, such as a pool heater or emergency generator that exceeds the capacity of the EFV. EFV replacement may be necessary if the EFV malfunctions (sticks open or closed). Industry experience is that EFVs rarely malfunction.


EFVs may not be installed on your service lines if:

  • The service line does not operate at a pressure of 10 psig or greater throughout the year;
  • The EFV could interfere with proper operation or cause loss of service;
  • An EFV could interfere with necessary operation or maintenance activities; or
  • The capacity of the meter on the service line exceeds 1,000 cubic feet per hour

If you request an EFV we will inform you if your service line meets any of these conditions.