Step-by-step fix
Step 1: Make sure the shutoff valve is really the problem
- Open the faucet and watch the shutoff valve under the sink while the water is running and again after the faucet is off.
- Look for water dripping from the valve stem, around the handle, at the compression nut, or from the valve body itself.
- Turn the valve handle off and on. If it will not fully stop water to the faucet, is frozen in place, or leaks from the body, replacement is usually the right fix.
- Check the faucet supply tube too. A leak from the supply tube nut or tube itself may need a new supply line instead of a new valve.
If it works: You have confirmed the shutoff valve is leaking, stuck, or not shutting off properly.
If it doesn’t: If the leak is clearly coming from the faucet supply line or the faucet above, fix that part first before replacing the valve.
Stop if:- The pipe coming out of the wall or floor is badly corroded, bent, loose, or moves inside the wall when touched.
- You see active leaking inside the wall, cabinet damage from long-term water exposure, or signs the pipe material is cracked.
Step 2: Shut off the water and drain the line
- Clear out the cabinet so you can work without twisting the pipe.
- Turn off the home's main water supply.
- Open the faucet served by this valve and leave it open to drain pressure from the line.
- Place a bucket or shallow pan under the shutoff valve and put towels around the work area.
If it works: Water flow at the faucet slows to a stop and the line is depressurized.
If it doesn’t: If water keeps running strongly, the main shutoff may not be closing fully and you will need to resolve that before removing the valve.
Stop if:- The main water shutoff will not close or is leaking heavily when operated.
Step 3: Disconnect the supply line and remove the old valve
- Use one wrench or pliers to hold the valve body steady and another to loosen the faucet supply line nut from the shutoff valve outlet.
- Let any remaining water drain into the bucket.
- Remove the old valve based on how it connects: loosen the compression nut on a compression valve, release the collar on a push-fit valve, or unscrew the valve from a threaded stub-out if that is what you have.
- Slide off old compression parts only if they come free without damaging the pipe. If the pipe end is scarred or out of round, cut back to a clean section if you have enough pipe length.
If it works: The old shutoff valve is off and the exposed pipe or threaded connection is clean and usable.
If it doesn’t: If the old compression sleeve or nut is stuck but the pipe is otherwise sound, use the matching replacement style that can work with the existing setup or use the proper removal tool before forcing anything.
Stop if:- The pipe starts twisting in the wall or floor while you loosen the valve.
- There is not enough solid pipe left to attach a new valve safely.
- Threads on the supply stub-out are damaged beyond cleanup.
Step 4: Match and install the new faucet shutoff valve
- Compare the new valve to the old one and confirm the inlet connection, outlet size, and angle or straight orientation match the existing setup.
- Install the new valve according to its connection style, keeping the outlet pointed where the supply line can reach without kinking.
- For compression-style valves, seat the valve squarely on the pipe and tighten the compression nut firmly while backing up the valve body. Do not overtighten.
- For threaded connections, start the valve by hand to avoid cross-threading, then tighten it securely while keeping the pipe stable.
- Make sure the new valve is in the closed position before restoring water.
If it works: The new valve is mounted straight, secure, and aligned for the faucet supply line.
If it doesn’t: If the valve does not seat squarely, the threads do not start cleanly, or the supply line no longer lines up, stop and correct the fit before turning water back on.
Stop if:- The new valve does not match the pipe connection or outlet size.
- The pipe is too short, damaged, or misaligned to support the new valve safely.
Step 5: Reconnect the faucet supply line and restore water slowly
- Reconnect the faucet supply line to the new shutoff valve outlet and tighten the nut while holding the valve body steady.
- Close the faucet above if you left it open for draining.
- Turn the home's main water back on slowly.
- Watch the new shutoff valve for a minute with the valve still closed, then open the shutoff valve slowly and let water flow to the faucet.
- Run the faucet for a minute to flush air from the line.
If it works: Water is restored, the faucet runs normally, and the new shutoff valve opens and closes smoothly.
If it doesn’t: If you see a small seep at a connection, shut the water back off and snug that connection slightly while supporting the valve body.
Stop if:- A connection sprays, the valve body leaks, or the pipe shifts when pressure returns.
Step 6: Verify the repair holds under normal use
- Dry the valve, supply line, and nearby pipe completely with a towel.
- Open and close the shutoff valve a few times to confirm it fully stops and restores water to the faucet.
- Check around the valve stem, inlet connection, and outlet connection with a flashlight after the faucet has run and again after it has been off for several minutes.
- Recheck the area later the same day for any slow seepage in the cabinet.
If it works: The valve stays dry, shuts off the faucet properly, and shows no leaks during use or after sitting under pressure.
If it doesn’t: If the valve works but a fitting still seeps, depressurize the line and retighten or remake that connection. If the valve body itself leaks, replace it with the correct matching valve.
Stop if:- You find recurring seepage from the wall-side pipe, hidden moisture, or movement in the stub-out that suggests a larger plumbing repair is needed.
Replacement Parts
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FAQ
How do I know which shutoff valve to buy?
Match the inlet connection to the pipe coming from the wall or floor, then match the outlet size to the faucet supply line. Also match the valve orientation, usually straight or angle, so the supply line reaches naturally.
Can I replace just the handle or packing instead of the whole valve?
Sometimes a stem packing nut can be tightened slightly, but if the valve body is leaking, frozen, or no longer shuts off fully, replacing the whole shutoff valve is usually the more reliable repair.
Do I need a new faucet supply line too?
Not always, but it is a good idea to inspect it closely while you are there. If the supply line is old, kinked, corroded, or the connection looks worn, replacing it at the same time can prevent another leak.
Why does the pipe need to be supported while I loosen the valve?
Without a backup wrench or pliers, the force can transfer into the pipe inside the wall. That can loosen fittings, crack older piping, or create a hidden leak behind the cabinet.
What if the old compression sleeve will not come off?
Do not pry hard against the pipe. Use the proper sleeve removal method or tool, or cut back to a clean section of pipe if there is enough length. Forcing it can damage the pipe and make the new valve harder to seal.