When & Why to Use 2-Stage Gas Regulators for buildings & Appliances

Two-stage gas regulator systems for buildings
- 2-stage gas regulators improve appliance operation in certain gas piping or building conditions
- LP or natural gas regulators or controls
- Gas regulator inspection, diagnosis, and repair guide
GAS REGULATORS for APPLIANCES - separate article
GAS REGULATORS for LP TANKS - separate article
GAS REGULATORS, TWO STAGE
Questions & Answers about using two-stage gas regulators on LP gas tank and fuel systems
References

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LP or natural gas regulator requirements: this article explains why, when, and where a two-stage gas regulator system is recommended at a building. Our page top photo shows a a large, remote, and centralized outdoor LP gas storage tank serving multiple homes in a small community in New York. A second LP gas regulator was required at individual buildings.

Recommendations for use of two-stage gas regulation for LP or Natural Gas fuel systems

In this article series we provide descriptions and photographs of unsafe gas piping, regulators, or controls on heating systems, indications of unsafe or improperly operating gas appliances, gas meters, and other gas installation defects. This document also provides free sample draft home inspection report language for reporting defects in oil and gas piping at residential properties.

Gas Cylinder or Tank Regulators: Readers concerned with installing, inspecting, or testing LP Gas regulators which are found on outdoor above ground or buried gas cylinders used for storage of LP Gas on site should also see How to Inspect & Test LP Gas Tank or Cylinder Regulators. Readers concerned with changing the fuel type between LP gas and natural gas for a gas fired appliance should see our safety warnings at Gas Conversion LP Natural Gas.

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.

Many residential LP gas installations will be found with a single gas pressure regulator at the storage tank.

A "two stage" LP gas regulation system uses two gas pressure regulators. Gas flows out of the LP Gas storage tank first through a "high pressure" regulation stage (usually installed right at the LP gas tank) and then through a second "low pressure" regulator as a second stage (usually installed close to the point of LP gas entry into the building). Two stage LP gas regulation is required for certain installations but is less often found installed at single family residential properties. Experts recommend this "two-stage" regulation of LP gas installations, particularly where large LP tanks are installed above or below ground for several reasons:

Large LP gas tanks will be located at a greater distance from the building
Two stages of LP gas regulation helps assure steady, even gas pressure at each appliance in the building, making it easier to maintain the requisite typical eleven inches of water (equivalent pressure) at each appliance. That's because the low-pressure regulator being used to deliver gas at the proper pressure for the appliances is located closer to the appliances than if it had been installed right at the more distant gas tank.
Two stage LP gas regulation can (slightly) reduce the LP gas system installation cost by permitting the use of smaller diameter gas piping between the first stage regulator (at the tank) and the second stage lower pressure gas regulator (at the building).
Two stage LP gas regulation helps avoid gas delivery system freeze-ups in climates where low temperatures are common, because the expansion rate and gas flow does not have to occur all at one place (at the final regulator). Distributing the pressure drop across two devices means less pressure drop occurs at each individual regulator device, reducing the tendency to form frost in very cold weather.
Use of two stage LP gas regulation permits a single high pressure line coming from the first regulator to deliver LP gas to multiple low-pressure regulators at diverse building locations, potentially improving LP gas appliance performance at a large building.
Service people assert that there will be fewer service calls due to loss of gas pilot flame or requirements for gas burner adjustment where two stage regulation has been employed on an LP gas piping system.

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.]

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Technical Reviewers & References

Related Topics, found near the top of this page suggest articles closely related to this one.

National Fuel Gas Code, ANSI Z223.1-yyyy - American Gas Association / National Fire Protection Association
LP-Gas Serviceman's Handbook,Fisher-Rosemount, Fisher Controls
National Fire Protection Association (NFPA) Pamphlets No. 54 and 58.
Specifications for Gas Installations, Central Hudson Gas and Electric Corporation
"Gaslight", Gary Quilliam, The Old House Journal, March/April 1989 article describes fixtures, modern fixtures, and sources of supply.
Residential Gas Hot Water Heater Pocket Partner - Testing and Trouble Shooting, 19. State Corp., Ashland City, TN 37015

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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.

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Recommendations for use of two-stage gas regulation for LP or Natural Gas fuel systems

Frequently Asked Questions (FAQs)

Ask a Question or Search InspectApedia

Technical Reviewers & References

Books & Articles on Building & Environmental Inspection, Testing, Diagnosis, & Repair