Gas piping in New Jersey (C) Daniel Friedman]Gas Piping Specifications

InspectAPedia tolerates no conflicts of interest. We have no relationship with advertisers, products, or services discussed at this website.

LP or Propane Gas Pressures & Natural Gas Pressure questions & answers:

Questions, answers, FAQs about the common operating pressures of natural gas and LP or liquid petroleum gas at the gas regulators, in building gas piping and at gas appliances.

This article series gives the standard pressure ranges and pressure settings for LP gas, propane gas, and natural gas fuels, including pressures found in the distribution service piping, in the in-building gas piping, and at gas fired appliances such as gas stoves, clothes dryers, furnaces, boilers, and LP gas or natural gas fired water heaters. Since there several ways that people express gas pressures we include more than on description of common LP gas or natural gas system operating pressures in this article.

Green links show where you are. © Copyright 2017, All Rights Reserved.

Gas Piping Materials, Sizes, Codes, Specifications for LP or Natural Gas in Residential Systems

LP gas valve at the LP gas tank or cylinder (C) Daniel Friedman

Question: James W. Howe on Size of Gas Piping Required

2016/09/26 James w Howe Jr said:

I was taught to ALWAYS use copper flex with LP gas and black pipe with NG. I'm am NOT talking about pressure here! That stated, my supply is two 100 lb tanks with an "automatic switch over valve". The lines from the tanks to the valve are 1/8th inch.

I need to feed a 30 inch 5 burner gas stove with a convection oven, a gas clothes dryer and a tankless 10L water heater that has a 1/2 inch gas inlet. Instead of running 1/2 inch copper flex with Ts to each appliance, do i need to increase the volume in the system to have enough gas to feed all three appliances.

If I was using NG, i'd install at least a ten foot piece of 1 1/4 black pipe to build up the volume and then run 1/2 inch Ts with 1/2 inch pipe to the appliances. With LP I'd use 3/8 copper flex for the dryer and stove and the 1/2 inch called for for the water heater, BUT, I need to get enough volume first so how should I proceed? All of the answers on your site deal with pressure and THAT is not the issue here!

Forgot my contact info:

[Click to enlarge any image]


Thanks for the comment and question, James, it helps us realize where we need to work on making our text more clear or more complete. A competent onsite inspection by an expert usually finds additional clues that would permit a more accurate, complete, and authoritative answer than we can give by email alone.

You will find additional depth and detail in articles at our website. See the ARTICLE INDEX link at the end of this article for a library of information about LP and natural gas piping, installations, equipment, pressures, regulators, etc. That said I offer these comments.

There's quite a list of types of piping material approved for use in gas piping systems; the distinctions I have seen are about the application - location such as above or below ground rather than the fuel difference between LP and NG; there have been, historically, opinions about gas piping and corrosion differences between the sources (thence the history of "dirt legs" on NG piping systems.

The list of gas piping materials - part of your question, depending on where the pipe is used, includes aluminum (in some locations and never below ground), brass (yellow - the old traditional gas piping found indoors in older buildings), copper type L or K rated for gas systems, iron (black ductile iron) above ground and possibly below ground in some jurisdictions, PE and PVC for outdoor underground use, and of course thinwall corrugated, coated flexible copper appliance connectors.

Watch out: Some jurisdictions such as New York City specifically prohibit use of some pipe materials such as cast iron, copper, brass, aluminum, and metallic tubing (with exceptions).

LP gas cylinder regulator in Two Harbors Minnesota (C) Daniel FriedmanI haven't seen pipe approval distinctions based on fuel but I think some opinions on that stem from differences in fuel moisture and contaminants, hence the "dirt leg" we see on older iron gas piping systems; I think that we don't see galvanized iron because corrosives in NG supplies may cause coating loss and clogging; at the end of the day it's the local plumbing inspector whose word is law.

See NFPA #58 adopted by many jurisdictions permitting either type of steel piping as long as it's certified to meet ASTM A53 steel pipe standards;

Here's an excerpt example from a local city gas code pertaining to natural gas piping. LPG regulations will sometimes differ.

New NG gas piping can be of Schedule 40 steel pipe with threaded fittings, Type L rigid copper tubing with brazed fittings, Type L soft copper tubing with flared fittings, or flexible CSST (corrugated stainless steel tubing) with manufacturer provided fittings. - City of Brownton, MN 55312 (outside Minneapolis/St. Paul MN).

Bottom line: to comply with piping materials choices you need to find out what local building or plumbing inspectors will accept as rules vary by jurisdiction.

I agree that 1/8" diameter is not likely to provide adequate flow rates to multiple appliances nor over distance. Typically the plumber connecting multiple appliances uses a larger line to bring gas into the building. Also see GAS PRESSURES LP vs NATURAL GAS - the home page for this topic. There we discuss gas pressure drop in long runs or small piping sizes. You’ll see that pressure and pipe size and delivery rates are connected. P1V1 = P2V2.

Even for short piping runs there are recommended minimum pipe diameters. None of them in current standards for gas piping is 1/8”.

Gas tank switchover valves for multiple LP tank installations

LP Gas tank pair (C) Daniel Friedman LP Gas changeover valve at

For other readers, Automatic or manual switchover valves: I’m indeed not sure that we’re talking about the same device, nor that it has to do with gas piping size and pressure.

Switchover valves used, e.g. in Australia, Canada, the U.S., the U.K. and other countries switch between two LP tanks so that as fuel runs low in one LP tank the homeowner can switch to the full tank. We also call those also “changeover valves”. A changeover valve is particularly useful when the empty LP tank is to be physically swapped-out for a full one.

Changeover valves are sold in both manual and automatic forms. Some changeover valves are combined with a gas regulator as shown in our photo above. Shown is a Winntec Model 6020 P1.0-15.6 Q6.R280 LP gaws regulator and changeover valve combined. This changeover valve is sold at plumbing and heating suppliers and at some RV suppliers such as

Reader follow-up: you do know what NPT stands for, right?

James Said:

Why do [-es everyone I ask] seem to have to always go back to talk about pressure. My run is only about 10 feet so pressure IS NOT an issue! I also have to guess that you are completely unfamiliar with an automatic switch over valve. I realize that they are seldom used anymore, but if you don’t have knowledge of them, you should have passed the question to someone who does.

The last i knew, I live in the good ‘ol USofA and in this country, we have something called the National plumbing Code. Since I am not a licensed plumber, i do not have a copy so asked a question of a website that I thought could give me a reasonable answer. To my dismay that is Not the case. Thanks, but no thanks, i’ll seek my answers elsewhere! By the way, the outlet on the automatic switch over valve is 1/2 inch NPT…you do know what NPT stands for, right? jwh,jr

Moderator reply: please be careful about quick, shallow "answers" to questions involving life-safety

Gas piping using piercing valve and copper tubing (C) Daniel FriedmanOf course pressure will be uniform throughout a system until appliances are using fuel. Then the pressure drop will depend on the length and size of piping. And use of a switchover or as we prefer changeover valve on LP tanks does not amend the requirements for gas piping sizing based on the flow requirements.

Sorry that our initial reply was confusing for you. We have readers in over 50 countries so we don't assume that we know where they live. "National Plumbing Code" itself is a standard that varies by country. But in the U.S., the National Plumbing Code is not the best resource for answering your question. Instead you'll want to see NFPA 54 that you can access for free, online. We include the necessary information to do so at the end of this article.

Sorry also to see you so aggravated that your email digresses to insults. We try our best to serve millions of readers a month, finding information if we don't already have it, researching for authoritative, unbiased sources and eschewing arm-waving opinion. Sometimes, depending on how your question has been worded, its length and content, we may not correctly understand the central question. 

We also understand the natural wish of a reader who says "never mind all that malarkey, just TELL ME THE ANSWER". But sometimes the questioner appears to us to be facing life safety hazards as well as building code and standard, permits, or licensing issues that we think requires a bit more information to come up with a reasonable and safe solution to a problem.

InspectAPedia is an independent publisher of building, environmental, and forensic inspection, diagnosis, and repair information provided free to the public - we have no business nor financial connection with any manufacturer or service provider discussed at our website.  

We are dedicated to making our information as accurate, complete, useful, and unbiased as possible: we very much welcome critique, questions, or content suggestions for our web articles. Working together and exchanging information makes us better informed than any individual can be working alone.

Watch out: It’s more important to understand that too high or too low gas pressures are unsafe, risking not just appliance malfunction but fire or explosion or fatal carbon monoxide poisoning.

For this reason, nobody, even the most generous plumber, if she or he has an ounce of sense, is going pretend that she can tell someone exactly what kind and size of gas piping is required for an installation about which she knows next to nothing. The danger of giving a person of unknown training and skill “how to” advice is that there is almost always one or more important considerations that an on-site expert would notice but that are not offered by the person asking the question. When discussing fuel gas piping there’s the ever present risk that the reader later blow himself up or catches his building afire. That caveat made we continue to try to help you out:

Reader follow-up: so answer my question: how big should my gas pipes be? Do I need a manifold with multiple outlets?

016/09/27 James W. Howe Jr. said

Insults? What Insults? I simply stated what I read into your answer. I STILL HAVE NOT GOTTEN AN ANSWER TO MY QUESTION! Which was since there is only a half inch outlet on the switchover valve, should I use black pipe with LP to increase the volume since even with the new products on the market for LP, I haven’t seen any that have a diameter larger than three quarters of an inch OR should I simply put a short manifold on the valve outlet with three half inch outlets on it and run three half inch lines, one to each appliance? jwh,jr

Moderator reply: excerpts on gas pipe diameter & length & BTUH or Cubic Feet per Hour Gas Supply for NG or LPG from model gas codes & resources

Buried LP gas line at wall (C) Daniel FriedmanJames:

Thank you for clarifying your question to focus on LP gas pipe size or diameter for a 10-foot length for an un-specified number of appliances or gas-fueled equipment.

Your original question mixed pipe type, pipe diameter, manifolds, fuels, tank changeover valves, and appliances of unknown input or BTUH requirements so we were not sure what answer would be most helpful.

You asserted that you’re asking just about pipe diameter and you don’t care about pressure, but it’s important to understand that it’s inadequate piping size (or improper regulators or regulator settings) that would deliver inadequate gas pressure (or flow rate in CFM per minute) at one or more appliances.

Typically the plumber measures gas piping pressure first with all appliances off, then with them on. If the pressure with all appliances using fuel falls below the required input pressure at the appliance regulators the plumber knows to choose among
increase pipe diameter size or to go to a two stage regulator system. A two stage regulator system is not normally required in a typical home gas piping installation.

You referred by email to lacking a copy of a model plumbing code such as the U.S. National Plumbing Code

As you’ll read CHAPTER 4, Gas Piping Installations, Section FGC 401, in the New York City Gas Code, found at - provided free at as well as by New York City, or as you can read in what’s the best resource about gas piping installation, the National Fuel Gas Code NFPA 54, proper sizing of gas piping cannot be decided by arm-waving, shouting, nor insult.

Rather one needs to do some simple arithmetic, looking at piping lengths, diameters, fuel type, AND the input BTUH (or cubic feet of gas per hour) required the appliances on the gas piping system.

Watch out: beware of a simple "just give me the answer" demand for questions that are incomplete, for which a safe proper answer requires more information, and for which a hasty one-size-fits'all answer could kill you or others.

I can't answer your gas manifold question as that's a local plumbing decision based on space, convenience, and other factors suggested here.

LP Gas Pipe Sizing Codes, Tables & Examples

Note that these data points are for 11" W.C. gas line sizing & copper. Different data will be obtained if you are designing a 2 psig gas line.

Gas Piping Sizing Codes, Specifications, Resources

In that reference you will see that for longer gas pipe runs, in excess of 100 feet, copper tubing in any size, 3/8" to 7/8" O.D. is not permitted and won't work.

Example Natural Gas Piping Code Excerpts

Here are a few explanatory excerpts from New York City's natural gas piping code; we provided some LP gas piping length examples in an earlier answer. :

401.3 Modifications to existing systems. In modifying or adding to existing piping systems, sizes shall be maintained in accordance with this chapter.

401.4 Additional appliances. Where an additional appliance is to be served, the existing piping shall be checked to determine if it has adequate capacity for all appliances served. If inadequate, the existing system shall be enlarged as required or separate piping of adequate capacity shall be provided.

401.3 Modifications to existing systems. In modifying or adding to existing piping systems, sizes shall be maintained in accordance with this chapter.

401.4 Additional appliances. Where an additional appliance is to be served, the existing piping shall be checked to determine if it as adequate capacity for all appliances served.
If inadequate, the existing system shall be enlarged as required or separate piping of adequate capacity shall be provided.

402.3 Sizing.Gas piping shall be sized in accordance with oneof the following:

1.Pipe sizing tables or sizing equations in accordance with Section 402.4.
2.The sizing tables included in a listed piping system’s manufacturer’s installation instructions.
3.Other approved engineering methods.
4.Individual outlets to gas ranges shall not be less than ¾ inches (19 mm) NPS .

402.4 Sizing tables and equations.Where Tables 402.4(1) through 402.4(5) are used to size piping or tubing,
the pipe length shall be determined in accordance with Section 402.4.1, 402.4.2 or 402.4.3.

402.4.1 Longest length method.The pipe size of each section of gas piping shall be determined using the longest length of piping from the point of
delivery to the most remote outlet and the load of the section.402.4.2 Branch length method.Pipe shall be sized as follows:

1.Pipe size of each section of the longest pipe run from the point of delivery to the most remote outlet shall be determined using the longest run of piping and the load of the section.
2.The pipe size of each section of branch piping not previously sized shall be determined using the length of piping from the point of delivery to the most remote outlet in each branch and the load of the section.

402.4.3 Hybrid pressure.The pipe size for each section of higher pressure gas piping shall be determined using the longest length of piping from the point of delivery to the most remote line pressure regulator. The pipe size from the line pressure regulator to each outlet shall be determined using the length of piping from the regulator to the
most remote outlet served by the regulator.


Using Schedule 40 Metallic Pipe and Natural Gas, where inlet pressure [at the appliance] must be less than 2 psi, the pressure drop in the system must be no less than 0.3" w.c. [Later tables in this reference allow grater pressure drop and then will support higher CFM of gas per hour for the same diameter and lengths of piping].

The codes I cite give detailed tables of pipe types, diameters, lengths, and the pipe's capacity to deliver some number of cubic feet of gas per hour. Take a look at your own appliances to see their requirements. Or you can look up typical appliance BTUH requirements in the documents we've cited.

402.5 Allowable pressure drop.The design pressure loss in any piping system under maximum probable flow conditions, from the point of delivery to the inlet connection of the appliance, shall be such that the supply pressure at the appliance is greater than or equal to the minimum pressure required by appliance.

403.1 General.Materials used for piping systems shall be new and comply with the requirements of this chapter or shall be approved.

403.1.1 Pipe size and pressure limitations.

1. All requirements for installation of gas distribution piping with operating pressures at ½ psig (3.5 kPa gauge) or less and above ½psig (3.5 kPa gauge) shall be in accordance with Chapter 4 of this code.

2. Gas distribution piping operating at a pressure of over ½psig (3.5 kPa gauge) to 5 psig (34.5 kPa gauge) and size 4 inches (102 mm) or larger shall be welded.Exception:Manufactured and listed gas trains provided with the appliance may be threaded

3. All gas distribution piping operating at a pressure above 5 psig (34.5 kPa gauge) shall be welded.

4. All welding of gas distribution piping shall be subject to special inspection as set forth in Section 406.

5. All piping 4 inches (102 mm) and greater operating at pressure exceeding 5 psig (34.5 kPa gauge) must be butt welded, subject to special inspection and radiographed.

6.Threaded piping may be used up to 4 inches (102 mm) at pressure no greater than ½psig (3.5 kPa gauge).

403.2 Used materials. Used pipe, fittings, valves and othermaterials shall not be reused.

403.3 Other materials.Material not covered by the standards specifications listed herein shall be investigated and tested to determine that it is safe and suitable for the proposed service, and, in addition, shall be recommended for that service by the manufacturer subject to approval by the commissioner.

403.4 Metallic pipe. Metallic pipe shall comply with Sections403.4.1 through 403.4.4.

403.4.1 Cast iron.Cast-iron pipe shall not be used.

403.4.2 Steel.Carbon steel and wrought-iron pipe shall be at least of standard weight and shall comply with one of the following standards:1.ASME B36.10, 10M2.ASTM A 53/A53M; or3.ASTM A 106.403.4.3 Copper and brass.Copper and brass pipe shall notbe used.403.4.4 Aluminum.Aluminum-alloy pipe shall not beused.403.5 Metallic tubing.Metallic tubing shall not be usedexcept as provided in Section 405.5

Watch out: There are life safety hazards involved when fooling with gas piping and appliances. Check with your local plumbing officials about what type of gas piping are permitted where you live, and while you’re at it, ask what gas piping or plumbing permits and safety and code compliance inspections are required where you live.

Article Series Contents

Natural Gas Appliance Operating Pressures in WC, millibars, Pascals, PSI or ounces of pressure

A common operating pressure for natural gas appliances is around 7 inches of water column (WC) or re-stating this in equivalent measure, that's 14.9 millibars or 1743 Pascals or Pa, or about 0.25 psi (pounds per square inch) or about 4 ounces of pressure per square inch.

LP or Propane Gas Appliance Operating Pressures in WC, millibars, Pascals, PSI or ounces of pressure

A common operating pressure for liquid petroleum or LP gas appliance is 10" - 11" of water column (WC) or re-stating this in equivalent measures, that's 27.4 millibars or 2491 - 2739 Pascals or Pa, or about 0.36 - 0.40 psi or about 5.78 to 6.36 ounces of pressure per square inch.


Continue reading at GAS PIPING, VALVES, CONTROLS - home, or select a topic from closely-related articles below, or see our complete INDEX to RELATED ARTICLES below.





Suggested citation for this web page

GAS PIPING SIZE & MATERIAL at - online encyclopedia of building & environmental inspection, testing, diagnosis, repair, & problem prevention advice.


Or use the SEARCH BOX found below to Ask a Question or Search InspectApedia


Frequently Asked Questions (FAQs)

Click to Show or Hide FAQs

Ask a Question or Search InspectApedia

Use the "Click to Show or Hide FAQs" link just above to see recently-posted questions, comments, replies, try the search box just below, or if you prefer, post a question or comment in the Comments box below and we will respond promptly.

Search the InspectApedia website

Comment Box is loading comments...

Technical Reviewers & References

Click to Show or Hide Citations & References

Publisher's Google+ Page by Daniel Friedman