How to Repair a Leaking Sink Shut-off Valve

An open view of the plumbing beneath a bathroom sink.
  • 1-3 hours
  • Intermediate
  • 20-60
What You'll Need
Masking tape
Slip-joint pliers
Small container
New washers
Clean rags

The shut-off valve under a sink can go unattended for years without giving any problems, but once it starts leaking, it can lead to a mess quickly. Ignoring minor leaks can waste up to three gallons of water every day and can also lead to permanent water stains and rot under your sink. However, calling a plumber can be expensive. So to save your valuable time, money, and water, here are a few easy steps to repair a leaking sink shut-off valve.

Step 1 - Tighten the Nut and Check

Wrap a masking tape around the jaw of your slip-joint pliers to avoid scratching and damaging the soft metal parts of the leaking shut-off valve. Then, use the pliers to grasp the nut positioned behind the valve handle and turn it slightly clockwise. Watch carefully to see if the dripping has stopped or has been reduced; this will indicate that tightening this nut is all you'll need to stop the leak. If the leaking does not stop, then proceed to the next step.

Step 2 - Turn Off the Water Supply

Shut off the main water supply to the sink you're working on and drain the pipes completely. Place a small container under the valve to catch any water left in the pipes that may come out while you're working

Step 3 - Dismantle the Shut-off Valve

Remove the screw from the shut-off valve handle with a screwdriver to dismantle it from the sink; it is not necessary to remove it from the supply line. After loosening the nut, pull out the threaded valve stem. Keep a careful note of the position and size of the washers.

Step 4 - Clean or Replace Washers

If the valve is not broken or cracked, then the source of the leak is almost always these washers. Mineral deposits built up on them can interfere their seal, and time can wear them down to the point where they are ineffective. So, you can either replace these washers with new ones of the same size or just clean them depending on your situation. Be sure to use a fresh rag to remove all the unwanted and patchy mineral deposits, and clean them gently without scratching or tearing them. Once they are done, they will become more flexible again, which will allow them to better serve their purpose.

Step 5 - Reassemble

Reassemble the valve and place it back on the sink, avoiding the use of any plumbing lubricants. These lubricants can stick the valve components together and make it difficult for you to conduct future repairs.

Turn on the water supply to the sink once the valve is back in place and the plumbing has been completely re-secured. As the line fills, watch out for leaks. At this point, if water is still exiting the valve, it will need replacement. Fortunately, a bad shut-off valve is extremely easy to replace. All you need to be careful about is that you must be able to find an identical shut-off valve to the old one with regards to the type, size, and thread.

Tip: While conducting any repair, it is essential to bear two things in mind. Always shut the drain before starting to prevent parts from slipping into the drain and pay attention to the order of each dismantled part to help in faster reassembly.