5 Reasons Why the shut off valve under sink won’t shut off water

Nothing could be more annoying on a winter morning than a dripping cold water pipe instead of the hot water pipe. Can you guess the problem? It is your shut-off valve. This valve controls the water supply and pressure. But the shut off valve under sink won’t shut off water if there is any leakage, burst pipe, stuck valves.

Normally, every household has two shut-off valves – main and local shut-off valves. Local shut-off valves are usually found under the sink in the washroom, and kitchen. You can use a new shut-off valve for 10-15 years, but they become prone to leakage and damage. Here we will discuss why isn’t the shut-off valve working and how you can fix it.

Shut Off Valve Under Sink Won’t Shut Off Water

If you are reading this article, then you must be having a terrible time with your plumbing system. First thing first! How can you be sure that your shut-off valve isn’t working? That is easy! Dripping of water won’t stop even after the closure of the pipe.

Before we dig into the solution, let’s glance at the most common shut-off valve problems.

why the Shut off Valve Won’t Shut off the WaterBest Applicable Solution
Damaged shut off valvesReplace with a new valve
Poor water sealCheck for the leakage and fix it
Stuck shut off valveLubricate the valve and again try to turn it on
Burst pipeMaintain the temperature in the winter
Sediment deposition Use vinegar and clean the sediment

Problem-1: Damaged shut off valve

A shut-off valve is a necessary addition to your plumbing system. The main and local shut-off valves are prone to rusting and cracking. So, it drips water all the time. Then what to do now?

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  • a new valve
  • pipe wrench
  • screwdriver
  • leather washer
  • adjustable wrench


  • If you are working on a local shut-off valve, don’t forget to close the main shut-off valve at first.
  • Then remove the old bonding jumper by losing and removing the coupling nut and nipple
  • Remove the old valve.
  • Install the new ball valve and a new leather washer
  • Tightly screw the nipple and the coupling nut.
  • Run the main shut-off valve and check if the newly installed valve can shut off the water when it is closed.

Problem-2: Poor water seal

Sometimes water keeps dripping from the sink even when there is no problem with your shut-off valve. The water seal may not be tightly fixed. Follow these simple tricks and get a hold of the problem.


  • Plier
  • Screwdriver
  • Replacement washer( if needed)


  • Check the condition of the water seal.
  • Use a plier and tighten all the joints.
  • If water still keeps dripping, replace the washer.
  • lose the nut at the base of the valve stem
  • Check the valve seat.
  • install a new washer
  • Screw the nut of the valve stem again.

Problem-3: Stuck shut off valve

Another common problem regarding the issue is the stuck shut-off valve. You will face this often when the valves get older and rusted.


  • WD-40 lubricant
  • Hairdryer
  • Plumber wrench


  • Start by shutting off the street-side shut-off valve.
  • Then spay the WD-40 lubricant on the stuck shut-off valve and wait for a few minutes.
  • Use a plumber wrench to check if the stuck valve is loosened or not.
  • If you find the valve is still stuck, use a hairdryer to heat the valve.
  • Then spray the WD-40 lubricant once again and keep monitoring.
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Problem-4: Frozen Pipe

People shut off the water supply in winter. The pipes freeze at 20 degrees Fahrenheit and eventually burst off.


  • Hairdryer


  • At first, try to find the frozen pipe location.
  • Gently apply warm air with your hairdryer.
  • Then shift from the lower frozen pipes.


  • Be careful of electrocution as you are working with a hairdryer on water.
  • Don’t switch on the valve suddenly if you find frozen pipes.


  • Install a thermostat in the house so that its temperature can keep the pipes warm in winter.
  • Insulate the pipes to survive the freezing winter.
  • Turn off the street-side faucets.
  • Keep the pipes under surveillance.

Problem-5: Sediment deposition

Minerals and fine sediments in water accumulate gradually, so your shut-off valve can only be partially closed.


  • Vinegar
  • Lubricant
  • Spray bottle


  • Close the water supply of the house.
  • Spray lubricant on the shut-off valve and uninstall the valve.
  • Mix vinegar and water in a 1:1 ratio in a spray bottle
  • Spray the solution on the sediments
  •  Wait for a few minutes and after that again install the valve the same way you install it.

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Frequently Asked Questions (FAQs)

How do you know if a shut-off valve is bad?

If the shut-off valve is bad, water will constantly keep dripping from the faucet. Moreover, you won’t be able to turn the water off after shutting off the local valves.

How do you fix water valve that won’t shut off?

If nothing can be done, then replace toilet shut off valve and install a new one. You can use a lubricant to rotate the stuck valve. Vinegar solution is proven useful for DIY sediment removal.

Final Verdict

You don’t always have to spend hundreds of bucks on maintaining a plumbing system. Your plumbing system will give an alarm about the problem. Like, the shut off valve under sink won’t shut off water if it’s damaged or clogged. So water keeps dripping constantly.

You should never overlook such problems. For example, if the valve isn’t working and you accidentally turn on the hot water line, you can scald yourself. It is installed as a protective measure against accidents and water loss.

So don’t hesitate to hire a professional plumber if troubleshooting is beyond your limit.

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