Laundry Valve Replaced Repaired

If the connections to the shut-off valves are visible, and you can see that they are threaded, you should be able to replace the valves using only a pipe wrench. Begin by shutting off the water to the laundry room – hot, cold or both depending on which valve you’re replacing. Disconnect the supply hose from each valve you’re replacing and open the valve to allow it to drain.
Tighten the wrench around the base of the valve using the hexagonal molding if there is one. Give the wrench a sharp counterclockwise jolt to break the thread seal and then unscrew the valve. If the valve is stuck, and you need more leverage, try extending the wrench handle with a length of 1-inch steel pipe.
Once the valve is off, clean the pipe threads with a wire brush and then wrap plumbing tape clockwise around the threads and screw on the new valve. Tighten it with a wrench, turn on the water and check for leaks before you hook up the supply hose for the washing machine.

Things Get Tougher When There's a Laundry Box

When the valves are installed in a plastic laundry box, you have to cut out a rectangular section of the wall to get to the connections. Use a drywall saw to cut through drywall or a keyhole saw to cut through wood. Save the cutout so you can repair the wall.
If the connections are threaded, you can theoretically use the procedure for replacing a threaded valve, but there may not be enough room for your wrench. In this case, a better solution is to cut the supply pipe about 6 inches below the box with a hacksaw and remove the old valve, pipe and all. This is also the best way to proceed if the valve is soldered to the pipe.
To install a new valve, either solder it or screw it to a length of new pipe. Drop the pipe through the hole in the washing machine box and connect it to the supply with a sweat connector or a compression coupler.