In this video, This Old House plumbing and heating contractor Richard Trethewey replaces a water supply shut-off valve.
1. Shut off the water leading to the valve being replaced.
2. Use emery cloth to buff clean the pipe on either side of the old valve.
3. Cut through the pipe on each side of the old valve with a mini hacksaw.
4. Slip new stop-and-waste valve into place between the just-cut pipe ends.
5. Grab hold of the valve with pliers and use an adjustable wrench to tighten one of the valve's compression fittings onto one of the pipe ends. Repeat for the other pipe end.
6. Turn the water back on, then open and close the new valve; check your work for leaks.