Fixture shut-off valves for copper plumbing pipes come in several styles. Some types have smooth sockets that are heat-soldered in place on the water pipe with a torch. Others are screwed onto threaded adapters that have been soldered permanently in place on the water pipe. A newer type of shut-off valve uses a grip-fit connection (often known by the common brand name, SharkBite). But one of the easiest types of shut-off valves to install is one that uses compression fittings.
Compression fittings are used for many types of pipe fittings, including unions, elbows, and transitions, as well as shut-off valves. They work by means of a brass compression sleeve that fits inside a coupling nut that screws onto the body of the valve. As the nut is tightened down onto the valve, it compresses the brass sleeve tightly against the copper pipe, creating a watertight seal.
Over time, fixture shut-off valves wear out. Fortunately, it is a very easy job to remove and replace a compression-type valve. Any time you are replacing toilet parts or a sink faucet, it's a good idea to test the operation of the fixture shut-off valves and replace them if necessary. It only takes a few minutes and ensures that the valves will work whenever you need them.
Most professional plumbers do not use compression shut-off valves: Under pressure, these valves can blow off, leading to potentially extreme water damage. Most experts prefer to solder valves instead, but for DIY repairs, a compression valve is functional.
When you buy a new shut-off valve, make sure the inlet size matches the diameter of your water pipe, and that the outlet size matches your flexible water supply tube. Fixture shut-off valves come in many variations, and it's a common mistake to buy the wrong size.
Equipment / Tools
- 2 channel-lock pliers
- Tubing cutter (optional)
- Compression sleeve puller (optional)
- New compression shut-off valve
Shut off the Water
The first step is to shut off the water supply to the house at the main shut-off valve, which is usually located near the water meter. (If you are replacing only a hot-side shut-off valve, then you could shut off the hot water at the water heater.)
It is considered good practice to replace both shut-off valves to a faucet at the same time. If one valve has gone bad, it's likely the other one will soon follow.
There will be some residual water in the pipe, so it is a good idea to have a small bowl, sponge, or towels handy when removing a fixture shut-off valve.
Remove the Old Valve
Disconnect the mounting nut that holds the flexible supply tube to the outlet nipple on the shut-off valve and remove the tube from the valve.
Disconnect the compression nut that fits around the water supply pipe by gripping the valve with one pair of channel-lock pliers and turning the compression nut with another pair of pliers. Slide the valve body off the end of the water pipe, then slide the brass compression ring and compression nut off the pipe. While the compression nut and ring could be reused with the new valve, it is better practice to remove these and install the new ones included with the new valve.
Because the compression sleeve has been squeezed against the pipe and, ideally, even changed the size of the pipe, it can be near-impossible to remove. (If the compression valve was installed properly, the sleeve should not come off.) If the sleeve does not come off with pliers, use a tubing cutter to cut back the copper and install the new compression valve on a new section of pipe.
Install the New Valve
With the old valve, sleeve, and compression nut removed, clean off the pipe with a rag. Slide the new compression nut onto the pipe, followed by the compression sleeve. Slide these pieces well down the pipe to make room for the valve.
Next, slide the valve onto the water pipe, making sure the pipe is fully seated into the valve's socket.
Slide the compression ring and nut up against the bottom of the valve and thread the compression nut onto the valve body. Tighten the nut as far as it will go by hand. Holding the valve with one pair of pliers, tighten down the compression nut with another pair of pliers. Another one-quarter turn of the nut with pliers is usually sufficient to fully tighten it.
Reattach the flexible water supply tube to the outlet on the valve. Tighten fully by hand, then another one-quarter turn with pliers.
Turn on the Water and Check for Leaks
With the shut-off valve fully closed, turn the water supply back on at the main shut-off valve. Check for leaks at the compression fitting on the valve. Slowly open the new shut-off valve while continuing to look for leaks at both the compression fitting and the flex tube fitting. If you see any water seeping, tighten down the nuts a little further until the leaking stops.
Compression valves can sometimes have slow leaks, and it is always a good idea to check back a few times in the hours after installation to make sure that there is no seeping water. If you notice a leak, shut the water off, remove the pressure from the line, then tighten the compression nut a little more and recheck it.