Gate valves operate to control the flow of liquids. In the home, the gate valve generally controls the flow of water throughout the home’s plumbing system. In fact, a gate valve is probably installed on the main water line that enters your home from the utility water meter. When a gate valve fails to open, chances are the single disc that seals the valve is stuck inside the valve body. When this occurs, the gate valve can be taken apart and reassembled in a few minutes.
Remove all pressure from both sides of the gate valve. You should be able to shut off the valve at the water meter outside. Open a water faucet to relieve the interior water system. It is best if you eliminate all pressure against the interior parts of the gate valve.
Loosen the top stem seal on the gate valve with the crescent wrench. The top stem seal is just below the handle on the gate valve. The top stem seal has a brass nut or nut housing. Close the jaws of the crescent wrench around the nut of the top stem seal.
Turn the crescent wrench counterclockwise. Do not remove the nut, only loosen it by one full turn or revolution.
Remove the crescent wrench from the gate valve’s stem seal nut. Attempt to open the gate valve now that some pressure on the single disc has been relieved. Turn the gate valve handle counterclockwise to open. If the gate valve opens, keep turning the handle until the handle can no longer be turned counterclockwise. Tighten the top stem seal nut on the gate valve, using the crescent wrench. If the gate valve will still not open, move on.
Loosen the top stem seal nut completely, using the crescent wrench. This will allow you to completely remove the single disc gate valve from the gate valve housing. Any liquid inside the valve or adjacent piping may leak when the disc is removed from the valve housing. Pull the disc from the valve and inspect. Chances are the disc may have been corroded into place and a little cleaning may repair the sticking. If not, the valve must be replaced.
Never operate a gate valve in a partially open position. The gate valve is designed to be used in either a fully open or fully closed position. Using a gate valve as a pipeline throttle will cause the valve to vibrate and become damaged. This damage will cause the valve seat not to seal properly.