How Do I Stop a Pipe From Leaking Under the Sink?
Last updated October 25, 2026
The short answer
Turn off the Water First
The first step is always to stop the flow of water. Look under the sink for two shutoff valves, one for hot and one for cold. Turn both clockwise until they stop. If there are no valves under the sink, locate the main water shutoff for your home, often near the water meter or where the main pipe enters.
Turning off the water prevents further damage and gives you a safe, dry space to work. After shutting off, open the faucet to drain any water left in the pipes. Place a bucket or towel under the leak to catch drips while you inspect the problem.
Find the Exact Leak Point
Dry all the pipes and fittings under the sink with a rag. Then turn the water back on briefly and watch closely. Common leak points are the slip joint nuts, the supply line connections to the faucet, and the drain trap. A drip may come from a loose nut or a worn washer.
If the leak is at a threaded joint, try tightening it with a wrench. Turn the nut clockwise, but only a quarter turn at a time. Over-tightening can crack plastic fittings or strip threads. If the leak persists, the problem may be a cracked pipe or a failed seal that needs replacement.
- Check the slip joint nuts on the P-trap
- Inspect supply lines for cracks or bulges
- Feel around the faucet base for moisture
- Look for corrosion or mineral buildup on metal fittings
- Test the drain basket seal for tightness
Tighten or Replace Fittings
For a loose connection, a simple tightening often stops the drip. Use an adjustable wrench or pliers, and hold the fitting steady with a second wrench to avoid twisting the pipe. For plastic fittings, tighten by hand first, then use a wrench gently. Do not use pipe thread tape unless you have removed the old tape and cleaned the threads.
If the pipe itself is cracked or corroded, you may need to replace a section. This involves cutting out the damaged part and installing a new piece with couplings. That job requires a hacksaw and pipe cutter, and it can be tricky in tight spaces. If you are not comfortable with that work, stop the leak with the shutoff valve and call a plumber or water damage pros.
Use a Temporary Patch for Emergencies
In an emergency, you can slow a leak with a temporary patch. For a small pinhole, wrap the pipe tightly with rubber or a piece of garden hose, then secure it with hose clamps. For a cracked joint, apply epoxy putty or pipe repair tape, which can seal for a short time.
These patches are not permanent fixes. They can give you hours to get a replacement part or call for help. Always keep the water shut off until the patch is fully applied and dry. After a temporary patch, plan to have the pipe properly repaired or replaced soon.
- Use rubber and hose clamps for a pinhole leak
- Apply epoxy putty for small cracks
- Wrap repair tape around a leaking joint
- Keep a bucket under the patched area
- Turn the water back on slowly to test
When to Call the Pros
Some leaks are beyond a simple DIY fix. If the leak is behind the wall, under the floor, or in a hard-to-reach spot, the damage may already extend beyond the pipe. Water can soak into cabinets and drywall, leading to mold and structural issues. In that case, you need professional help to find and fix the source.
The pros can locate hidden leaks, dry out affected areas, and repair water-damaged materials. They have the tools to detect moisture behind surfaces and the experience to handle complex pipe repairs. If you live in Layton, keep your shutoff valve location written down so you can act quickly in an emergency. For cleanup after a leak, professional drying and dehumidification may be necessary.
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Call (801) 383-0232 any time, day or night, and describe what happened.
Call Now (801) 383-0232Frequently asked questions
What if the leak is coming from the drain pipe?
Drain leaks often come from loose slip joint nuts or a worn rubber gasket. Tighten the nuts gently, or replace the gasket. If the pipe is cracked, replace that section. The drain is not under pressure, so the leak may be slower but still needs attention.
Can I use duct tape to stop a pipe leak?
Duct tape is not a reliable fix for a water pipe. It may hold for a few minutes, but water pressure will push through. Use rubber and hose clamps or pipe repair tape for a temporary seal. For a lasting repair, replace the damaged part.
How do I know if the leak caused damage?
Check for soft spots in the cabinet floor, warped wood, or a musty smell. Water can travel along pipes and soak into walls. If you notice any of these signs, dry the area thoroughly and consider a water damage inspection to check for hidden moisture.