How to Work with Gas Pipes | Ask This Old House

Ask This Old House plumbing and heating expert Richard Trethewey explains how gas piping is installed in a home.

Skill Level: Expert – for licensed professionals only

Steps:
1. In general, residential houses start with 1” gas pipes at the gas meter and then branch out to smaller diameter pipes using T fittings as they reach their appliance destinations.
2. To connect gas appliances to the main branch, there are gas pipes that come in a variety of lengths that you can piece together to reach each appliance. They are secured with pipe dope and gas fittings. Because of the way the threads work, piping always has to start at the source and work its way outward towards each appliance.
3. It’s also possible to thread your own gas pipes at the exact length you need if you have a pipe threading tool.
4. Before turning the gas back on, any professional will test for leaks by connecting a manometer to the pipes, locking in the air pressure, and waiting overnight to see if the pressure drops.
5. If the new gas work passes the manometer, a soap test should also be done as the gas is turned back on. If the soap solution bubbles over any of the new work, that means there is a leak.

Resources:
Richard emphasizes that only a licensed professional should work with gas. The materials they use for gas pipe fittings, including the pipes, nipples, and pipe dope, can be found at home centers and plumbing supply houses.

About Ask This Old House TV:
Homeowners have a virtual truckload of questions for us on smaller projects, and we're ready to answer. Ask This Old House solves the steady stream of home improvement problems faced by our viewers—and we make house calls! Ask This Old House features some familiar faces from This Old House, including Kevin O'Connor, general contractor Tom Silva, plumbing and heating expert Richard Trethewey, and landscape contractor Roger Cook.

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How to Work with Gas Pipes | Ask This Old House

[jordancook]

“Gas should only be done by a licensed professional, so now I’m going to show you how to do it on YouTube.”

[melissacowan]

My 4 year old son faithfully watches your show! Richard is his favorite. His current favorite videos are any of the toilet repairs, gas line, hvac and leaky duct work. Richard, he doesn’t believe you’re real, he thinks you only exist on YouTube. Thanks for your clean, informative videos that provide great content for my little guy. Melissa from Wyoming

[-old-Forthischet]

About forty something years ago, I moved my gas fired water heater from inside the house to an outside heater closet. My then brother-in-law had a whole cart for making gas pipes including a manual thread making jig. Because money was tight back then, I did it myself by reading "how to" books (the internet wasn't born yet). That house is still standing by the way, after I sold it about 30 years ago.

[shortliner]

Having enough volume and pressure being delivered to the appliance means everything with gas. Before I retired in 2016, I worked for the gas utility company in Baltimore. Sometimes we'd have a distribution problem when a large building converted from oil or coal to gas and a larger service pipe was tapped into the main to supply the new heating plant. Occasionally, there would be too much demand on the main between the new and existing customers when the new heating system would cut on and the main pressure would drop too low from insufficient gas volume. We'd then have to do a system reinforcement installation to boost the gas supply requiring either a larger main being laid for the new service or tapping a nearby higher pressure main and installing a pressure regulator station and back feed main tapped into the old main near the customer's service pipe. The same is true with a building having multiple gas appliances - you have to have the correct size pipe so that each appliance gets a sufficient supply of gas volume at the pressure required even when all the appliances are operating at the same time.

[AndrewGray]

He keeps talking about "the old days" like we aren't still out here cutting and threading pipe. We only buy 21 foot sticks and nipple trays. More couplings = more potential leaks, more $$$ in fittings.

[chrisgoldbach]

Thank you guys. We need your teachings in schools.

[Danny-fshk]

Richard is such a great teacher! Thanks for another very informative video.

[aerial]

I remember my dad having me use his manual pipe threader a number of few drops of oil every full turn and stop after so many threads shown out the end the threader...

[williamwinder]

To seal gas fittings I use Leak Lock or Expado if the threads are messed up. Had tightened a 4" pipe with Expado with no problems.

[worldview]

Always appreciated from your team 👍👍👍👍

[jimjordan]

I just replaced a faulty (as in old and frozen) cut off valve to a space heater. Installed new brass cut off and made up a manifold with nipples and tees for a pressure test port, try additional cut off valves and BIP to new space heater. Checked and no leaks. Everything works great. Ran out of pipe dope on the last three connections so I used some Bondo. Great stuff that Bondo! Really handy! LOL. Just kidding! Just thought I'd let a few heads explode! LOL

[oldtwinsna]

Richard is an expert in anything gassy.

[joejr]

What old days, we still cut and thread gas pipe all the time. Also when checking for a leak use kids bubbles. They work better than solutions you buy from supply houses.

[tj_gsomething_]

Thanks for showing us what not to do unless we're licensed professionals.

[twfbyzh]

This was funny on multiple levels good times.

[jasonclark]

You should do a diy on how to cut in a lasco BLACK R&L NIPPLE, COUPLING and TEE for installation of a gas line addition on a pre-existing gas line in a homeowners home for maybe a natural gas or propane fireplace, bbq or even a laundry dryer gas line. Cutting in a R&L nipple and TEE on pre-existing gas lines doing remodeling can be daunting if you don't know how to make a job easier and more cost effective and their is no need to cut a lot of holes from one end of the house and removing pipe near the location your going to be adding a gas line addition in your home, you just cut a hole close to your remodeling location and cut in a R&L nipple, coupling and TEE also go over how adding a gas line can change you BTU's at your gas meter and make sure a license Plumber or contractor is using proper code for their City and state guidelines. 🤓

[juniormint]

Gee Rich, in the old days the old timers didn't screw around with soap, they'd just use their torch flame to leak check, plus it would bake the dope in ensuring a leak free joint.

[glocksantana]

Love the smell of burning pipe cutting oil in da morning

[VaxxedStories]

Do they make couplings with threads reversed on one end?

[mrsoccergod]

Can you use thread tape instead of the dope on the threads