We recently took out an outdated gas insert and looking to have a simple decorative firebox.

As a temporary measure I put a metal screw cap with some yellow Teflon tape on the gas pipe in the firebox.

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The gas pipe goes down to the basement where it connects to flexible piping before connecting back to the black gas line (the tap is closed).

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From what I have read I just need to unscrew where the flexible piping connects to the black gas line and place the cap there instead.

It's a 100-year old home so there isn't a gas shutoff valve inside the property, just at the meter instead. I'd prefer not to mess with that valve unless required.

  • Is this something an amateur can do safely?
  • Is it reasonable to not have the gas supply to the house turned off, or is that asking for trouble?

If the answer is to get a gas technician in then so be it, but if it's a simple job I can safely do in a few minutes then even better.

  • 2
    Be careful plugging the hole in the hearth where the pipe currently comes out; whatever you use needs to be pretty robust, and to NOT drop burning ashes into your basement. Mar 23, 2016 at 22:38
  • @DanielGriscom Do you have any recommendations? I have some high-heat mortar but as you say I can imagine it'd just fall straight down. Is there a suitable material to plug the gap with and then inject the fireplace mortar on top?
    – user118412
    Mar 24, 2016 at 20:10

2 Answers 2


You have the right idea. Just remove the flexible pipe and transfer your cap to the fitting on the shutoff valve.

  • Make sure you leave the shutoff valve in the off position.
  • Make sure you have the correct threads and seal them and the connection is tight.
  • Check for leaks with a thick solution of soapy water.
  • If at any time you feel uncomfortable or think things are not working out right then shut off the outside valve and call a pipe fitter.

Good luck!

  • 1
    Do not reuse the cap, install a new one. The threads on these fittings deform a bit when tightened, so they should not be reused.
    – Tester101
    Mar 23, 2016 at 23:14

I would remove the flexible line and the adapter fitting that's screwed into the valve and replace it with a MIP plug.

I can't tell from the photo, but it's probably 1/2", maybe 3/4". It might say on the valve body. This one is brass, but you can use black iron pipe, too. http://ecx.images-amazon.com/images/I/41S-R8BeMkL.SL500.jpg

You'll need two adjustable wrenches. One to hold the valve to keep it from turning while you use the other to remove the fitting.

Put some pipe joint compound on the plug threads, screw it into the valve and tighten it down good.

Open the valve and drip soapy water in the joint and check for bubbles. Re-tighten until no bubbles appear. Shut the valve.

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