How to Identify & Correct LP Gas or Natural Gas Leaks
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This document describes how to find gas leaks on LP or natural gas piping, regulators, or appliances, and it provides free sample draft home inspection report language for reporting defects in oil and gas piping at residential properties. Here we provide descriptions and photographs of unsafe gas piping, indications of unsafe or improperly operating gas appliances, gas meters, and other gas installation defects are provided.

General safety warning: improper installation and even improper inspection and testing methods involving natural or "LP" gas can involve dangerous conditions and risk fire or explosion. If you smell gas you should leave the building immediately and should do so without doing anything that could create a spark such as operating a light switch or telephone. From a safe location, call your gas company's emergency line and/or your fire department. The text provided here is a working draft and may be incomplete or inaccurate.

Contact us to suggest text changes and additions and, if you wish, to receive online listing and credit for that contribution. Also see How to Report Defects in Oil Piping.

NOTICE: while example report language is provided here, reproduction of this or any of our web pages or their contents at other websites or in printed documents for sale is prohibited.

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How to Test or Look for LP Gas System Leaks

Here we outline some common procedures used to test gas piping and fittings for leaks. These procedures should work equally well for both LP gas (propane or bottled gas) systems and for natural gas (piped-in gas from a gas utility company) systems.

NOTE: Except that LP gas and natural gas operate at different pressures and thus will have different test pressure specifications. Readers who are interested in gas leak detection equipment should review our article and gas testing warnings at Recommendations for gas measurement instruments & gas detector tubes for indoor gas level tests which includes our description of use of the TIF8800 and similar gas detectors.

Safety Warnings for Gas Leaks

if there is evidence of an LP or natural gas leak: at a building, gas odors, for example, you should:

• Do not do anything that is likely to cause a gas explosion, such as lighting a match, operating an electrical switch, or even using a telephone in the building
• Leave the building immediately
• Notify other building occupants of the safety concern
• Contact the local gas company and/or fire department

Pressure testing a gas piping system for evidence of gas leaks

These two methods are generally used to test a gas piping distribution system to see if leaks are present.

• Low Pressure Method Gas leak tests by gas service technicians generally include the following steps:
• All gas piping connections, valves, and appliance connections and valves are inspected visually for tightness and good condition
• A gas pressure gauge [such as the Fisher(TM) Type 50P-2 gas pressure gauge] is connected to a burner orfice
• The gas service valve is opened to permit gas to flow into the gas piping distribution system, and then the valve is closed again, securely
• The gas pressure gauge should read eight inches of water column in pressure (previously 9 inches, earlier eleven inches of water column) and should hold steady.
• The gas pressure at the point of testing, say a gas-fired heating appliance, is bled off slowly until the gas pressure test instrument gauge indicates nine inches of water column.
• The system is monitored for any pressure drop for at least three minutes. If no pressure drop is detected the system is considered not leaking.
• High pressure gas leak method is also used by gas service technicians and includes steps similar to those above, using a special fitting [such as the Fisher(TM) Type J600 test block] installed between the service valve outlet port at the LP gas tank. The service valve is opened,as above, to pressurize the gas piping, and the system is bled down to a test pressure of 10 psig, then monitored for at least three minutes to check for a pressure drop.

Thanks to reader Tony Martinez for updating our data on the proper pressure for LP or Natural Gas leak testing.

Methods used to find and identify points of gas leaks in a gas piping distribution system or at a gas appliance

• Gas odors observed during gas piping inspection: The mercaptan put into LP gas and natural gas is inserted there by the gas company as a safety feature so that people may notice that they have a dangerous (explosive) gas leak in their home. Some people may confuse this odor with a septic tank gas odor. See Diagnosing and Curing Sewer Gas Smells and Septic Tank Odors for a discussion of sewer gas odors.
• "Soap solution" bubble tests for gas leaks: a solution of soapy water (some technicians use dish soap and a brush or rag) is the most common method used to test for gas leaks. As we noted earlier, Readers who are interested in gas leak detection equipment should review our article and gas testing warnings at Recommendations for gas measurement instruments & gas detector tubes for indoor gas level tests which includes our description of use of the TIF8800 and similar gas detectors.
• Soap solution is applied at every piping joint or connection (or the test instrument may be used carefully at and around every connection or other suspect point) and the technician watches the soaped connection to see if soap bubbles are formed. Experts warn that this method requires some experience and care. For example, a large gas leak may blow away the solution without forming a soap bubble, or bubbles may be forming in a location which is physically hard to see.(Sometimes we can "see" around a corner or to the back side of a pipe using our TIF 8800 combustible gas detector in these cases.)
• Soap solution is applied along gas piping to lengths of piping to test for pinholes or mechanical damage if no leaks are found at threaded or flared connectors but when gas leaks are evident in the system.
• Gas leaks at gas valves: we very often find very small gas leaks at the seamed sides of some gas valves, such as those commonly found on gas-fired domestic water heaters, especially when using the TIF 8800. These leaks can be so miniscule that they do not show up during a bubble test, and they are often present even on new valves. This may be a source of some disagreement between a home inspector, building owner, and the gas service technician, and need to be handled with some judgment, experience, and reason.

Identifying Sources of Leaks at Brass Flare Fittings on LP Gas Piping Systems

Here are two brass flare fittings. One of them had a gouge that gave us a gas leak that was a bit tough to find until we disassembled and inspected the leaky joint. If tightening flared copper tubing connections does not easily correct a leak at that joint, do not just over-tighten the joint (you may break the flare and cause a still larger leak), and do not rely on pipe sealant inside of flared copper tubing fittings.

Open and inspect the flare fitting joint, and replace the flare fittings or make a new copper tubing flared end if necessary.

LP Gas Piping Defect list and sample home inspection report language

Safety warnings about gas piping: Check condition of flexible gas line connections: Caution: we do not pull out appliances to look at gas line connections, but you should do so, checking condition of flexible connections for leaks and assuring that a shutoff valve is installed. Watch for leaks in those flex-connector lines between gas line and the appliance as they are thin wall and often corrode and leak. Gas leaks are dangerous.

Safety warning. Flexible soft copper piping has been used to supply municipal (natural) gas to the
... electric clothes dryer.
... hot water heater.
... heating system.
This is not a recommended installation and it may be prohibited by local codes - "black iron" steel piping is required in many jurisdictions.

Safety warning: Flexible ridged thin wall copper tubing has been used to supply gas to the
... hot water heater.
... heating system.
This is not a recommended installation and it may be prohibited by local codes.

Technical Violation: Flexible copper LP gas line may not be routed through walls or similar locations where it may be damaged or punctured. For these sections of routing threaded iron pipe is required. This is an usually inexpensive item to correct. You can discuss this point further with your gas supplier and your plumber.

All gas or oil piping must comply with local codes and ordinances or with the national fuel gas codes. Copper and brass tubing (except tin lined copper) shall not be used if the gas contains more than an average of .3 grains of hydrogen sulfide per 100 standard cubic feet of gas.

National Fuel Gas Code, 1988 articles 2.6.2, 2.6.3, & 3.4.2 "Piping in Partitions". Also NFPA 58 Code. See ANSI Z223.1-NFPA 54.
Residential Gas Hot Water Heater Pocket Partner - Testing and Trouble Shooting, State Corp., Ashland City, TN 37015

*** Safety Recommendation: support the loose gas lines: gas lines> additional support is needed to secure the building appliance gas supply line at
___
Loose gas lines can lead to dangerous leaks. This item should be addressed soon and should be a minor cost.

Gas Piping Maintenance Tips

*** Safety:We recommend that unused gas equipment be removed and that you have the unused section of gas line properly sealed by a qualified plumber or by your gas supplier. Leaky old appliances or gas lines are dangerous.

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GAS PIPING, VALVES, CONTROLS
  Gas BTUH & Cubic Feet
  Gas Conversion LP Natural Gas
  Gas Flame & Noise Defects
  Gas Leak Detection
  Gas Lighting Pipes & Fixtures
  Gas Meters
  Gas Piping Defects
  Gas Regulators for Appliances
  Gas Regulators for LP Tanks
  Gas Shutoff Valves
  LP Gas Tanks
  LP & Natural Gas Safety Hazards
  Natural Gas Combustion Products
  Types of Fuel Gas Source

• U.S. Energy Information Administration - eia.doe.gov/
• U.S. Environmental Protection Agency - epa.gov/solar/energy-and-you/affect/natural-gas.html
• At Natural Gas.Org www.naturalgas.org/environment/naturalgas.asp#emission you’ll find a table of combustion products
• At geocities.com/rainforest/6847/report1.html is an interesting and detailed though not “neutral” report on the components and contaminants in the combustion of natural gas. You’ll see a long long list of emissions products, but look again – most of the contaminant levels listed are in the picograms.
• apvgn.pt/documentacao/iangv_rep_part1.pdf lists the components in natural gas exhaust from vehicles
• The Need Project, Manassas, VA: need.org/needpdf/infobook_activities/SecInfo/NGasS.pdf
• Kroschwitz, Jacqueline I., and Mary Howe-Grant (eds.). "Gas, Natural." In Encyclopedia of Chemical Technology. 4th ed., vol. 12. New York: John Wiley and Sons, Inc., 1993.
• Tussing, Arlon R., & Bob Tippee. The Natural Gas Industry: Evolution, Structure, and Economics. 2nd ed. Tulsa, OK: PennWell Publishing, 1995.
• Thanks to reader Tony Martinez for technical editing regarding the test pressures for gas leak evaluation - 3/19/2010.

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