How to Shorten a Gas Pipe to Fit an Oven

When a licensed professional shortens or runs new gas pipe, they typically work with schedule 40 black steel pipe — a reliable conduit that has been used in residential gas systems for about 100 years. The pipe is available in pre-cut lengths in increments as small as half an inch, so a pro can build the run almost like an erector set without needing to cut and thread every piece on site.

Pro Tip: Richard, This Old House plumbing and heating expert, warns that if you ever smell gas in your home, you should get out of the house immediately and call 911. Natural gas is normally odorless, but utilities add a chemical called mercaptan so you can detect leaks by smell.

Steps:

1. Working with gas is dangerous and should be left to a licensed professional.
2. Start by shutting off the gas to the meter using a wrench.
3. Carefully slide the stove out until you can fit behind it to break the connections.
4. Disconnect the flexible gas line from the gas piping using the pipe wrenches.
5. With the pipe wrenches still in hand, loosen the gas piping and the shutoff from the pipes below the floor. Since gas pipes usually go in before any finish work happens, there’s a chance that twisting the pipe will damage the wall a little behind it when the shutoff begins to twist.
6. Unthread the gas pipe from the shutoff valve.
7. Replace the gas pipe with a smaller pipe. Be sure to choose a size that’s long enough to reach all the way through the floor, but short enough to allow for the additional height of the flexible gas line to the stove. To thread the pipe, apply a generous coat of pipe dope to the threads and be sure to tighten it using the pipe wrenches.
8. With the shorter pipe secured to the gas shutoff, apply more pipe dope to the thread on the other side of the short pipe. Send it back through the floor and tighten it to the rest of the gas line using the pipe wrenches. Be sure to tighten it until the gas shutoff is parallel to the wall so you’re still able to access the shutoff as needed.
9. Reconnect the flexible gas line from the stove to the shutoff on the pipe. Slide the stove back into place.
10. Turn the gas back on. Test all the new work for leaks by applying a soap solution along all the new connections. If any bubbles form in the solution, it means air is escaping somewhere and the connections aren’t sealed tightly enough. If there are no bubbles, then the gas line is perfectly sealed.

Pro Tip: After turning the gas back on and testing your new connections with a soap solution, remember that shutting off the entire gas supply to the house may have allowed air into other lines. As shown in a This Old House project, the plumber purged each individual line to every appliance in the house — not just the stove — to make sure each one was operating safely before considering the job complete.

Measuring for the Right Pipe Length: Before removing the old pipe, note the height of the ledge or floor surface where the pipe emerges. In a This Old House project, the plumber placed a witness mark on the existing pipe at the ledge height — about 11.5 inches off the floor — to ensure the replacement pipe would be short enough for the flexible line to connect while still reaching through the floor. Black steel gas pipe comes in pre-cut lengths in increments as small as half an inch, and shorter pieces called nipples are available from 1.5 inches up to 12 inches, so you can find a size that fits precisely without needing to cut and thread on site.

Resources:
Richard emphasizes that working with gas is extremely dangerous and should be left to a licensed professional.

All of the tools and materials Richard used to shorten the gas pipe, including the replacement nipple, pipe dope, pipe wrenches, and the soap test, can all be found at home centers.

Tools