Natural Gas -- Sediment Trap

The sediment trap in a natural gas service line is required by code in most jurisdictions for most gas appliances. Sections 408.4 of the ICC Fuel Gas Code and 9.6.7 of NFPA 54 require a sediment trap except for illuminating appliances, ranges, clothes dryers and outdoor grills. As with any code the local authority having jurisdiction can override or modify the code requirement. Some jurisdictions have expanded the requirement to assure the installed sediment trap is functional. Some photos of various observed sediment traps reveal the need for more education or stricter codes because not all traps are properly installed.

According to GAMA, "The trap shall be constructed to change the direction of the gas flow by 90 degrees." This seems to be overlooked by many installers. Installing a sediment trap in a horizontal section of pipe will not trap as much sediment as installing it where the gas flow changes directions. The optimal, as diagramed by the 2006 NFPA 54, installation of the sediment trap is at the point where the gas flow is downward and makes a 90 degree change of direction. No examples of this optimum installation have been found by the author. It is supposed that if the flow is down, more sediment will drop into the trap than will fall out of the flow if it is up.

Briggs and Stratton Home Standby Power Generator installation instructions show the gas flow in an upward direction at the sediment trap. The Generac Home Standby Power Generator installation manual suggests a sediment trap but does not show an example. The Generac installation DVD does not mention or show a sediment trap.

Much thought must be put into a natural gas piping installation to facilitate the optimum sediment trap. Typically the builders heating and air conditioning contractor installs the gas piping to a capped stub near the generator. The generator installer is typically responsible to continue the gas supply to the generator. This involves the shutoff valve, the sediment trap and a convenient plug that can be tapped for pressure measurement. Close cooperation is required to end up with the generator flex and the sediment trap in an optimum configuration. The generator installer should specify the exact location for the capped gas supply pipe.

References

• Most codes and standards are protected by Copyright so rather than directly quote the text, links below reference the standards.
• Excerpt from the 2007 Supplement of the International Fuel Gas Code that quotes sediment trap section 408.4.
• 2004 GAMA News Release about Sediment Traps that includes the NFPA 54 sediment trap diagram.
• The 2006 NFPA 54 National Fuel Gas Code Section 9.6.7 defines requirements for sediment traps and offers a method of installation in figure 9.6.7.
• View NFPA codes including the National Fuel Gas code by entering "online access" in the NFPA.org search box. Then follow the instructions to view any of the NFPA codes.
• Several state building codes are available at Free eCodes from the International Code Council (ICC).
• GAMA is the national trade association of manufacturers of residential, commercial and industrial appliances and equipment, components and related products.