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 (EFV)

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.

Customer Owned Lines

Safety is Everyone’s Responsibility:

Federal Regulation 192.16 requires that we notify you to exercise diligence regarding underground or buried gas piping. Buried pipe may be subject to leakage and/or corrosion (corrosion may occur on metallic pipe) and could potentially be subject to hazards if not maintained.

Buried gas piping should be:

  • Periodically inspected for leaks;
  • Periodically inspected for corrosion if the piping is metallic;
  • Repaired if any unsafe condition is discovered, or the flow of gas should be shut off;
  • Located and marked in advance when excavation is performed or is about to be performed near the buried gas piping;
  • Excavated by hand when work is performed near the pipe.

Our Part

Middle Tennessee Natural Gas owns, operates and maintains the Natural Gas distribution pipeline in our District, up to and including the Natural Gas meter. We do not own, operate or maintain gas piping downstream of the meter, though we are available to assist customers with their fuel line needs. We are required to notify you of the lines that belong to you, and your responsibilities under Federal Regulation 192.16.

Your Part

Any and all gas pipe downstream of the Natural Gas meter (the "building" side) belongs to you, the gas customer. It is the gas customer who is responsible for maintenance and operation of this portion of the fuel line system. We do not own the gas beyond the meter; therefore, we do not maintain or locate fuel lines. Commercial plumbers and/or heating contractors, including our own Customer Service Department, may be contacted when gas fuel lines need attention.

If you have any questions or comments, please feel free to contact us.

Pipeline Safety

Whether you are building an addition, laying a patio, planting a garden, or just digging a post hole for a mailbox, Don't Dig Though the Natural Gas Service Line. Should you plan to do any digging, please contact TENNESSEE ONE CALL - THE STATEWIDE NOTIFICATION SERVICE by calling 811 at least three days in advance so that all Middle Tennessee Natural Gas owned buried pipe may be located and marked for you at no charge.

All digging in the vicinity of piping should be carefully done by hand. This will avoid the inconvenience of disrupted service, personal injury and expensive repairs.

Violation of the "Call before you Dig" Act is a Class A misdemeanor and subject to a fine up to $2,500 and/or imprisonment for 48 hours.

If a gas main or service line is exposed during digging, call Middle Tennessee Natural Gas. Proper attention to pipe that has been exposed will prevent problems later.

Natural Gas Facts

The properties of Natural Gas actually combine to make it the safe, clean and environmentally friendly energy choice for the 21st Century.

Natural Gas is…

  • A naturally occurring mixture of several light hydrocarbons and other gases. The primary ingredient in Natural Gas is methane, composed of one part carbon and four parts hydrogen (CH4).
  • Lighter than air and non-corrosive.
  • Odorless and colorless in its natural state. So, for safety reasons, an odor that smells like rotten eggs is added to Natural Gas so that you can smell it, allowing leaks to be located and repaired.
  • Gaseous at any temperature over -260 degrees Fahrenheit.
  • Non-toxic and contains no poisonous ingredients, though in large quantities in enclosed spaces it can displace oxygen.
  • Clean burning: methane burns easily and leaves few pollutants. When natural gas is burned properly, by-products of combustion are primarily carbon dioxide and water vapor. Because methane contains only one carbon atom, natural gas produces less carbon dioxide than any other fossil fuel, and fewer other pollutants as well.
  • Safer to handle than most fuels. Natural Gas by itself will not burn. Combustion can occur only when there is a proper mixture of gas and air; a flammability range comprised of approximately 5 to 15 percent natural gas, and between 95 to 85 percent air. Even with the proper mixture it requires a high ignition temperature of approximately 1,100 degrees Fahrenheit.
  • A strong greenhouse gas, so burning it and producing carbon dioxide is actually preferable to allowing it to release into the atmosphere.

All of these factors combine to help make Natural Gas the safest energy source available. Understanding and following proper safety practices help make it even safer.

Carbon Monoxide

Carbon monoxide can result from the incomplete combustion of any fossil fuel. Natural gas appliances are designed and installed in a manner to eliminate this concern, if operated properly. As with all energy, careful diligence must be exercised with natural gas. Appliances must be properly operated and maintained to insure your safety. The information on carbon monoxide below is adapted from the Centers for Disease Control and Prevention website; for additional information visit

Appliance Safety

Natural gas appliances should always be:
…installed by properly trained and qualified personnel.
…installed in accordance with installation instructions and applicable building codes.
…converted from propane use only by qualified personnel according to instructions.
…operated and maintained according to manufacturer’s instructions.
…inspected regularly to insure proper operation.

MTNG will gladly perform a safety inspection or “light-up” of a newly installed appliance, and will repeat inspection annually upon request at no charge.

Appliance safety points to consider between inspections include the following: clearances, filters, flammables, unvented heaters, vents & ducts, water heater reliefs, and water temperature.

When selecting a natural gas appliance, please remember that there are special considerations for installations in bathrooms, bedrooms, garages, and more. Please contact us if you have questions or concerns. Our trained professionals are always happy to make recommendations that could help prevent any potential problems.

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