How to Fix a Leaking Pipe Under the Sink

A leaking pipe under the sink can feel stressful, especially when you notice water pooling inside your cabinet. But the truth is, most under-sink leaks are not complicated to fix.

In fact, this is one of the most common issues covered under DIY Plumbing Repairs, and many homeowners successfully repair it themselves without calling a plumber.

If you act quickly and follow the correct steps, you can prevent cabinet damage, mold growth, and expensive service calls.

Step 1: Identify Where the Leak Is Coming From

Before touching anything, dry the area with a towel. Then place a dry paper towel under each connection and run the faucet for a minute.

Check carefully for moisture around:

• Pipe joints
• P-trap connections
• Supply lines
• Shut-off valves
• Cracked PVC sections

Finding the exact source is important because not all leaks require the same fix.

Step 2: Turn Off the Water Supply

Before repairing anything, shut off the water.

Under the sink, you’ll usually see two small valves one for hot water and one for cold. Turn both clockwise until they stop.

Then turn on the faucet to release any remaining pressure.

This step prevents sudden water spray while working.

Step 3: Tighten Loose Connections

Many leaks happen because a connection has loosened over time.

Using an adjustable wrench, gently tighten the nut at the leaking joint. Do not overtighten. PVC pipes can crack if too much force is applied.

After tightening, turn the water back on and check again.

If the leak stops, the repair is complete.

Step 4: Replace Worn Washers or Gaskets

If tightening does not solve the issue, the rubber washer or gasket inside the joint may be worn out.

Steps to replace:

1. Turn off water supply.
2. Unscrew the leaking joint.
3. Remove old washer.
4. Insert new washer of same size.
5. Reconnect and tighten gently.

Washers are inexpensive and available at most hardware stores.

Step 5: Fix a Small PVC Crack

If the pipe itself has a small crack, you have two options:

• Temporary repair using waterproof pipe repair tape
• Permanent fix by replacing the damaged section

For a quick temporary fix, wrap pipe repair tape tightly around the crack.

For permanent repair:

1. Remove damaged pipe section.
2. Measure and cut replacement piece.
3. Apply PVC primer and cement.
4. Reconnect securely.

Step 6: Check for Supply Line Leaks

Sometimes the leak comes from flexible supply hoses.

If the hose is corroded or cracked, replacing it is simple:

1. Turn off water supply.
2. Disconnect old hose.
3. Install new braided stainless-steel hose.
4. Tighten securely.

Preventing Future Under-Sink Leaks

• Avoid overtightening connections
• Check under sink every few months
• Replace old hoses every 5–7 years
• Keep cabinet dry and ventilated

Common Mistakes to Avoid

• Ignoring small drips
• Overtightening plastic fittings
• Using wrong washer size
• Forgetting to shut off water

Small mistakes can turn a simple repair into a bigger problem.

When Should You Call a Plumber?

While most under-sink leaks fall under DIY Plumbing Repairs, you should call a professional if:

• Pipe is severely corroded
• Wall plumbing is leaking
• Water damage is extensive
• You cannot identify leak source

Estimated Cost Savings

Professional service call: $150–$400

DIY repair cost: $10–$50

Doing it yourself can save significant money.

FAQ – DIY Plumbing Repairs

1. Is a leaking pipe under the sink dangerous?

It can be if ignored. Water damage can cause mold and cabinet rot. Fix it quickly.

2. How long does this repair take?

Most small repairs take 20–45 minutes.

3. Can I use duct tape for pipe leaks?

Duct tape is only temporary. Use proper pipe repair tape or replace the section.

4. Why does my pipe leak only when I run water?

This usually indicates a drain pipe joint issue rather than supply line leak.

5. How often should I inspect under my sink?

Every 3–6 months is a good habit.

Final Thoughts

Learning basic DIY Plumbing Repairs gives you confidence as a homeowner. Fixing a leaking pipe under the sink is one of the easiest and most cost-effective repairs you can handle yourself.

With simple tools and careful steps, you can protect your home from water damage and avoid unnecessary service costs.

Stay proactive, inspect regularly, and don’t ignore small drips. Small problems are always easier to fix early.