How to Replace a Shutoff Valve

Stop under-sink leaks with this 30-minute fix.

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Replace a leaky shutoff valve

Old shutoff valves often develop leaks when you shut them off to install or repair a plumbing fixture. Whenever you replace or work on a fixture, check the shutoff valves and replace them if they look old or are hard to turn. Turn off the water at the water main. Open a basement faucet and the faucet above your shutoff valve. We show you how to replace a shutoff valve that's soldered to a copper water line. If you have galvanized steel or plastic supply lines, buy the appropriate shutoff valves for your system. Disconnect the faucet supply lines (Photo 1). If you have compression fittings, unscrew the compression nut and remove the old valve. If your fitting is soldered on, you can cut it off, but chances are there won't be enough pipe left to attach a new valve. Photo 2 shows how to unsolder an old fitting with a propane torch. Use a flame protecting cloth to keep flammable surfaces inside the cabinet from burning. Sand off remaining solder with an emery cloth, and then proceed to Photo 3 to hook up the new valve.