Many sinks have two shutoff valves underneath: one for cold water and one for hot. Closing the appropriate valve lets you service a faucet or stop a local leak without shutting down the whole house. If a valve is corroded, leaking, or seized, do not force it.
Identify the hot and cold supply valves
Each valve normally connects a wall pipe to a supply line leading to the faucet. If they are not labeled, run one side of the faucet and gently close one valve to identify which supply it controls.
Close the valve without forcing it
Wheel valves take several turns, while lever valves are often quarter-turn. If the handle resists strongly, use the main shutoff rather than applying force that could snap the stem.
Open the faucet to release pressure and confirm shutoff
After closing the valve, open the matching faucet side. A little residual water may flow and then stop; continued flow means the valve is not sealing or the wrong side was closed.
A leaking shutoff needs repair before faucet work
If the valve begins leaking at the stem or connection when moved, stop and control the leak. Replacement requires shutting water off upstream, usually at the main.
Sources
- U.S. Environmental Protection Agency WaterSense — Home Maintenance — Household maintenance related to water, leaks, toilets, pressure, and efficient use.