|
|
How to find leaks in gas piping: How to Identify & Correct LP Gas or Natural Gas Leaks
|
InspectAPedia tolerates no conflicts of interest. We have no relationship with advertisers, products, or services discussed at this website.
Detect or find gas leaks in natural gas or LP gas / propane piping, fittings, & appliances: This article 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. This article series provides descriptions and photographs of unsafe gas piping, indications of unsafe or improperly operating gas appliances, gas meters, and other gas installation defects are provided.
Green links show where you are. © Copyright 2013 InspectAPedia.com, All Rights Reserved. Author Daniel Friedman.
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.
Watch out: 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.
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.
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.
Our photo at above left of an LP gas line shutoff shows black staining around the shutoff valve and flare fitting, with some of the black worn away - previously there had been an LP gas leak at this location. |
General Safety Warnings for LP or "bottled" or "propane" Gas Installations & Inspections
Immediate LP or natural gas safety hazards: 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 and keep a safe distance away - 100 feet or more.
- Notify other building occupants of the safety concern
- Contact the local gas company and/or fire department
Heating equipment which the inspector (or building occupant or manager) judges to be an immediate life safety hazard should be shut down and appropriate emergency services called.
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™ 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. Thanks to another reader JR, an industry manager familiar with gas pressures, who adds that these two fuel gases operate at different pressures. In residential appliances
- Natural Gas system pressure: Natural gas operates at a nominal pressure of 7” WC (about 0.253 psi)
- LPG or Liquid Propage Gas system pressure: LP gas or propane operates at a nominal pressure of 11” WC (about 0.397 psi)
- Actual NG or LPG gas pressures vary: [Note: the exact pressure you see in the building at an appliance may vary from these numbers depending on the gas distribution piping system size, diameter, number of appliances served, number of appliances operating, regulator adjustment, and other factors. See Gas Regulators for Appliances and Gas Regulators for LP Tanks. See LP or Natural Gas Pressures for a table showing the range of variation
in LP gas pressure in the tank at various temperatures. - Ed.]
and adds:
Watch out: Extinguish gas pilot lights - in order to perform pressure-testing methods for LP or natural gas leak detection as discussed above, you will need to extinguish the pilot lights on all gas-fired appliances in the building, and the pilot lights will need to be re-lit again after testing is complete.
Methods used to find and identify points of gas leaks in a gas piping distribution system or at a gas appliance
|
Visual Inspection for Evidence of Gas Leaks in fuel gas lines and appliances:
Our photograph shows black stains on copper tubing at the flare fitting connecting an LP gas line to a shutoff valve.
Some service technicians
point to stains on piping as an evidence of a possible chronic leak in the gas line at this point. |
- 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.
Also see Advice for Making Flare Fitting Connections with Copper Tubing or Piping where we describe preparation of the flare joint for flexible copper tubing for refrigeration or gas piping lines.
Frequently Asked Questions (FAQs)
...
Ask a Question or Search InspectApedia
Questions & answers or comments about troubleshooting LP gas or natural gas leaks in gas piping or appliances .
Ask a Question or Enter Search Terms in the InspectApedia search box just below.
Technical Reviewers & References
Related Topics, found near the top of this page suggest articles closely related to this one.
- 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
- 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.
- Thanks to reader JR for discussing LP and natural gas operating pressures and leak detection safety, October 2010.
Books & Articles on Building & Environmental Inspection, Testing, Diagnosis, & Repair
 The Home Reference Book - the Encyclopedia of Homes, Carson Dunlop & Associates, Toronto, Ontario, 25th Ed., 2012, is a bound volume of more than 450 illustrated pages that assist home inspectors and home owners in the inspection and detection of problems on buildings. The text is intended as a reference guide to help building owners operate and maintain their home effectively. Field inspection worksheets are included at the back of the volume. Special Offer: For a 10% discount on any number of copies of the Home Reference Book purchased as a single order. Enter INSPECTAHRB in the order payment page "Promo/Redemption" space. InspectAPedia.com editor Daniel Friedman is a contributing author.
Or choose the The Home Reference eBook for PCs, Macs, Kindle, iPad, iPhone, or Android Smart Phones. Special Offer: For a 5% discount on any number of copies of the Home Reference eBook purchased as a single order. Enter INSPECTAEHRB in the order payment page "Promo/Redemption" space.
|
|
