Back Button

How to Cap a Gas Line in My House

Damon Koch

Most gas lines used in homes are composed of black steel or iron, also called black pipe. When there is a gas line in your home that is no longer being used, it must be capped to ensure the safety of the home's residents.

Even if there is a shutoff valve before the termination point, a cap must be installed in order to ensure there is no gas leakage in case of a valve failure.

  1. Turn off the gas supply from the closest shutoff valve or at the gas main.

  2. Thread the end of the pipe with a pipe threader if the pipe is not already threaded. Insert the end of the pipe into the threader and turn the threader clockwise until about an inch of the end of the pipe has been threaded. Remove the pipe threader from the end of the pipe.

  3. Smear pipe dope onto the threads to help seal the connection when the cap is installed.

  4. Twist the cap onto the end of the pipe by hand until it is snug. Turn the cap clockwise to install it on the end of the pipe.

  5. Attach a pipe wrench to the gas line 6 inches below the cap. Use another pipe wrench to turn the cap while holding the gas line securely in place. Tighten the cap completely. Restore gas service.