The short answer
Turn off the Water First
Before you touch anything, locate the shutoff valves under the sink and turn them clockwise to stop the flow. If there are no valves there, shut off the main water valve for the house. Test the faucet to confirm the water is off before you start working.
Keeping the shutoff valve location written down helps in a hurry. In regions with wet winters, knowing how to stop water fast can save your floors and cabinets. Once the water is off, place a bucket or towels under the sink to catch any remaining drips.
Tighten Loose Connections
Most kitchen sink leaks come from loose nuts or fittings. Use a wrench to gently tighten the supply lines where they connect to the faucet and the shutoff valves. Do not overtighten, as that can crack the fittings and make the leak worse.
You can also check the sprayer hose and the base of the faucet. If you see water pooling near the handle, the faucet O-rings may be worn. Tightening these connections often solves the problem without needing to replace any parts.
- Use a basin wrench for hard-to-reach nuts
- Wrap plumber's tape on threaded connections
- Check the sprayer hose for cracks
- Tighten the faucet base if it wiggles
- Look for water stains under the sink
Inspect the Drain Seal
The drain assembly under the sink can leak where the basket strainer meets the sink basin. Remove the drain pipe and clean the old putty or plumber's putty from the flange. Apply a fresh bead of putty and reinstall the strainer, tightening the locknut from below.
Also check the rubber gasket between the strainer and the sink. If it is cracked or flattened, replace it with a new one from a hardware store. This is a common fix for a leak that appears only when the sink is full of water.
Replace Worn Washers and Gaskets
If the leak comes from the faucet spout or handle, the internal washers or cartridges are likely worn. Turn off the water, disassemble the faucet handle, and inspect the rubber washers. Replace any that look flattened, cracked, or brittle.
For a single-handle faucet, you may need to replace the entire cartridge. Take the old cartridge to a hardware store to find a matching replacement. Reassembly is the reverse of removal, but make sure all parts are seated correctly to avoid new leaks.
When to Call the Pros
If you have tightened everything and the leak persists, or if the water has already damaged the cabinet floor or walls, it is time to call local water damage pros. They can detect hidden moisture in the subfloor and dry out areas that are hard to reach.
Professional help often includes moisture mapping and structural drying to prevent mold. Acting quickly reduces the chance of long-term damage to your kitchen.
Water damage does not wait
Call (425) 407-5186 any time, day or night, and describe what happened.
Call Now (425) 407-5186Frequently asked questions
What if I can't find the shutoff valves under my sink?
If there are no valves under the sink, find the main water shutoff for your house, usually near the water meter or where the pipe enters the home. Turn it off before any repair. Write down that location for future emergencies.
Is it safe to use plumber's tape on all connections?
Plumber's tape works on threaded pipe connections, but not on compression fittings or plastic push-fit connections. For those, use the manufacturer's recommended sealant or simply tighten carefully. Overusing tape can cause leaks if applied incorrectly.
How do I know if the leak is from the drain or the supply line?
Dry the area completely, then run water through the sink and watch. If the leak appears only when the drain is full, it is likely the drain seal. If it leaks when the faucet is on, check the supply lines. If it drips continuously, it is probably the shutoff valve or the faucet base.