Kitchen Sink Leak Repair: How to Fix Leaks Under Your Sink (Step-by-Step)

💧 From dripping connections to cracked pipes—complete guide to finding and fixing kitchen sink leaks yourself

You reach under the kitchen sink to grab a cleaning bottle, and your hand touches something wet. You pull out a soggy cardboard box. Water is dripping from somewhere—but where? Your heart sinks. A kitchen sink leak can mean water damage, mould, and ruined cabinet floors.

But here’s the good news: most kitchen sink leak repair jobs are simple and DIY-friendly. A loose connection that needs tightening. A worn washer that needs replacing. A supply line that’s cracked. Most fixes take 15-30 minutes and cost R50-R200 in parts.

I’ve repaired thousands of kitchen sink leaks over the years. The key is identifying where the leak is coming from—faucet, supply lines, or drain pipes—then applying the right fix. This guide will walk you through every step.

For related information, read our kitchen sink installation guide, how to fix a leaking pipe guide, and water leak repair services guide. Let’s stop that leak.

🔍 How to Identify the Leak Source

Before you can fix leaking sink issues, you need to find where the water is coming from:

1. Clear out the cabinet – Remove everything from under the sink.
2. Dry everything thoroughly – Use towels to dry all pipes, connections, and the cabinet floor.
3. Place paper towels or dry cloths – Position them under potential leak points.
4. Run water – Run the faucet, fill the sink, then drain it. Watch where water appears first.
5. Check different scenarios – Check with faucet running, sink full (draining), and dishwasher running.
6. Feel for moisture – Run your hand along pipes and connections (water may be warm if from hot supply).

Common leak locations:

• Faucet base (water on top of counter or dripping down)
• Water supply line connections
• Basket strainer (where sink meets drain)
• P-trap and drain pipe slip nuts
• Dishwasher drain hose connection

Read our leak detection services guide for help finding hidden leaks.

🚰 Leak #1: Faucet Base (Water on Countertop)

If water pools around the faucet base on your countertop or drips down the outside of the sink, the faucet base seal has failed.

Symptoms: Water on countertop around faucet, water dripping down outside of sink, damp cabinet floor near faucet area.

Common causes:

• Loose faucet mounting nut
• Failed O-ring or gasket at base
• Cracked faucet body (less common)

DIY fix:

1. From under the sink, tighten the faucet mounting nut (use a basin wrench if space is tight).
2. If tightening doesn’t work, remove the faucet and replace the base gasket or O-ring.
3. Apply plumber’s putty under the new faucet base before reinstalling.

Time: 15-30 minutes. Cost: R50-R200 for new gasket/putty.

Read our leaking kitchen tap fix guide for more faucet repair details.

💧 Leak #2: Water Supply Lines

Leaks from the hot or cold water supply lines are common—and usually easy to fix.

Symptoms: Water dripping from flexible hoses or at connection points. May be hot or cold water depending on which line is leaking.

Common causes:

• Loose connection nuts
• Worn rubber washer inside connection
• Cracked or bulging supply line (replace immediately—risk of burst)
• Cross-threaded connection

DIY fix:

1. Turn off water supply at isolation valves.
2. Tighten the connection nut gently—1/4 turn with wrench (don’t overtighten).
3. If still leaking, turn off water, disconnect, and inspect the rubber washer. Replace if worn (R5-R20).
4. If the supply line is cracked or bulging, replace it (R50-R150).
5. Turn water back on and test.

🥣 Leak #3: Basket Strainer (Sink Drain)

The basket strainer is the metal drain fitting inside the sink. Water leaking from here indicates a failed seal.

Symptoms: Water dripping from the underside of the sink drain, visible water around the basket strainer nut.

Common causes:

• Loose lock nut
• Failed plumber’s putty or silicone seal
• Cracked basket strainer

DIY fix:

1. From under the sink, tighten the large lock nut (use channel locks or a basin wrench).
2. If still leaking, the putty has failed. Remove the basket strainer, clean off old putty, apply fresh plumber’s putty, and reinstall.
3. If the strainer is cracked, replace it (R100-R300).

Time: 30-60 minutes. Cost: R50-R300 depending on parts needed.

🔧 Leak #4: P-Trap or Drain Pipes

Leaks from the drain pipes (P-trap) are common and usually easy to fix. This is a classic pipe leak scenario.

Symptoms: Water dripping from slip nuts, wet pipes, water pooling under the P-trap.

Common causes:

• Loose slip nuts
• Worn or missing slip nut washers
• Cracked pipe (especially old PVC)
• Misaligned pipes causing poor seal

DIY fix:

1. Place a bucket under the P-trap.
2. Tighten slip nuts gently—hand-tight plus 1/4 turn (don’t overtighten plastic nuts—they crack).
3. If still leaking, remove the slip nut, inspect the washer (replace if worn, R5-R20), and reinstall.
4. If the pipe is cracked, replace the damaged section (R50-R200 for new pipe/fittings).

Time: 15-30 minutes. Cost: R5-R200.

Read our how to fix a leaking pipe guide for more pipe repair techniques.

🍽️ Leak #5: Dishwasher Connection

The dishwasher drain hose connects to your sink drain or garbage disposal. This connection can leak.

Symptoms: Water appears only when the dishwasher is running, not when using the sink.

Common causes:

• Loose hose clamp
• Cracked or damaged hose
• Clogged dishwasher wye (causing backflow)

DIY fix:

1. Tighten the hose clamp with a screwdriver.
2. If the hose is cracked, replace it (R100-R300).
3. Check that the dishwasher wye isn’t clogged—clean if needed.

Read our dishwasher installation guide for more details.

🛠️ Tools & Materials You’ll Need

For most kitchen sink leak repair jobs, you’ll need:

Read our plumbing tools guide for more equipment information.

📋 Step-by-Step Repair Guide for a Leaking Kitchen Sink

Here’s a general approach for how to repair a leaking kitchen sink:

1. Identify the leak source – Use the drying method in Section 1.
2. Turn off water supply – Close isolation valves under the sink.
3. Place a bucket – Position it under the leak area to catch drips.
4. Disassemble if needed – Loosen the leaking connection.
5. Inspect parts – Check washers, O-rings, and threads for damage.
6. Replace damaged parts – New washers are cheap—replace them.
7. Clean threads – Remove old tape or debris.
8. Apply fresh tape or sealant – Use plumber’s tape on threaded connections.
9. Reassemble and tighten – Hand-tight plus 1/4 turn (don’t overtighten).
10. Turn water on and test – Run water, check for leaks, dry the area, and check again after 10 minutes.

📞 When to Call a Professional

While most kitchen sink leak repair jobs are DIY-friendly, call a pro if:

• You’ve tightened connections and replaced washers, but the leak persists
• The leak is coming from inside the wall (not under the sink)
• You find extensive water damage or mould
• The pipe is cracked and needs soldering (copper pipes)
• You’re uncomfortable with any step
• The leak returns after multiple repair attempts

Professional cost: R750-R1,500 for standard leak repair. In Sandton or Fourways, rates may be higher.

For emergency service, use our 24/7 emergency plumbing services.

🛡️ Preventing Future Kitchen Sink Leaks

Prevent sink leak under sink issues with these habits:

• Check under the sink monthly – Run your hand along pipes, look for moisture.
• Don’t overtighten connections – Hand-tight plus 1/4 turn is enough.
• Replace supply lines every 5-10 years – Rubber hoses degrade over time.
• Use plumber’s tape on threaded connections – Prevents leaks at threads.
• Avoid hanging heavy items on pipes – Stress can loosen connections.
• Don’t pour grease down the drain – Solidifies and can crack pipes.

Read our home plumbing maintenance checklist for a complete schedule.

❌ 5 Costly Mistakes to Avoid

📋 Real-World Kitchen Sink Leak Case Studies

❓ Frequently Asked Questions About Kitchen Sink Leaks

✅ Final Thoughts: Small Leaks, Big Savings

A dripping kitchen sink might seem minor, but it wastes water, damages your cabinet, and can lead to mould. The good news? Most kitchen sink leak repair jobs are simple and cheap—a loose nut needing tightening or a R5-R20 washer needing replacement.

Key takeaways for South African homeowners:

• Identify the source first – Dry everything, then run water to see where it drips
• Most leaks are loose connections – Try tightening gently first
• Washers are cheap (R5-R20) – Replace them whenever you disassemble a connection
• Don’t overtighten – Hand-tight plus 1/4 turn is enough
• Never ignore a small leak – It will get worse and cause damage
• DIY saves R750-R1,500 – Most simple leaks are fixable in minutes
• Call a pro for wall leaks, cracked pipes, or persistent leaks

Your action plan: Clear out under your sink. Dry everything. Run water and watch. Identify the source. Tighten first. If that doesn’t work, replace washers. If the leak persists or is in the wall, call a professional through ServiceLink SA.

For more information about kitchen sink leaks and plumbing repairs, explore our related resources:
kitchen sink installation guide,
how to fix a leaking pipe guide,
leaking kitchen tap fix guide,
water leak repair services guide,
and kitchen sink leak repair guide.
Our how ServiceLink SA works and
contractor verification process pages explain how we connect you with trusted professionals.
See our service areas page for leak repair coverage in your region.