Replace a valve in copper pipe
If you have to replace a leaky valve, it can be difficult to spread the cut section wide enough to insert the new valve. The solution is to use a special “slip” or “no-stop” coupling (available at home centers for less than $3). Unlike traditional couplings, no-stop couplings don't have a flange or dimple that stops the plumbing pipe once it’s inserted halfway into the coupling. This lets you install the coupling and move it back out of the way, then have room to insert the new section of pipe. Turn off the water, then cut the pipe about 6 in. from each side of the leaky valve, using a pipe cutter or a hacksaw. Place the no-stop coupling over the existing pipe. Cut a new section of pipe to replace the piece you cut out (be sure to factor in the length of the water valve). Solder the pipe to the valve, then stick the assembled section between the two existing pipes (Photo 1). Move the no-stop coupling over the new pipe, then solder all the joints (Photo 2).
The standard or “stopped” couplings have indentations, which stop the copper pipe when inserted. The “no-stop” coupling doesn’t have indentations.