How to Fix a Leaking Kitchen Sink

Dealing with a kitchen sink leaking underneath can be frustrating. A kitchen sink leak can waste water and damage your cupboards, so it’s important to act quickly when you spot a problem.

Thankfully, we can guide you through the process of fixing a leak under your sink. Whether you have a leaking pipe under the sink or worn-out washers, this practical guide helps you tackle the job.

We’ve also included a handy video to show you exactly how to stop a kitchen sink from leaking. With the right tools and a little patience, you can get your kitchen back in working order.

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Tools

Materials

Kitchen Sink Waste & Overflow Kit

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To find a leak under a kitchen sink, check all pipes for moisture, hand-tighten the compression fittings, and fill the plugged sink with cold water to see if the level drops.
A leaking sink drain is generally caused by the plastic seals or washers between the sink and the strainer becoming old, perished, or damaged.
You can fix a leaking sink by turning off the water supply, removing the trap and waste pipe, cleaning the area, and installing a new strainer and washers.

Why is my kitchen sink leaking?

Before you can fix a kitchen sink leak, you need to know what’s causing it. A leaking sink is generally caused by the washers. These are the plastic seals between your sink and the strainer, and over time they become old, perished or damaged, leading to water escaping. This is the most common reason for a kitchen sink leaking.

How to find a leak under a kitchen sink

Firstly, try and work out where your leak is coming from. Check all the pipes underneath the sink, including both the cold and hot tap feeds. Look closely for any signs of drips or moisture.

Next, hand-tighten the compression fittings. Then test the sink for leaks again.

If the kitchen sink leak continues, test the washers. Simply fit your plug and fill the sink with cold water. If the water level goes down, you almost certainly need to replace the washers. This helps you pinpoint the exact location of the sink leaking underneath.

How to repair a leaking sink

It helps to be prepared before you repair a leaking sink. It’s best to store the manufacturer's instructions for your sink and taps somewhere safe as this information may help you to locate the source of the leak. It also helps you solve the problem as quickly as possible.

No specific safety equipment is required, but it’s a good idea to be careful of sharp edges when removing the plughole. Take care when cleaning the area around the sink hole too.

Start by turning off your water supply before you do any plumbing work. To do this, locate the stopcock and turn it clockwise.

Remove any cabinet doors that may block your access. You need a clear view of the pipes and the underneath of the trap as this makes it easier to fix the leak under your kitchen sink.

Place a bucket or watertight container underneath the trap to catch any water that may spill out during the repair.

Unscrew the two compression fittings that hold the waste pipe in place. You may need to use a wrench if the compression fittings are particularly tight. Carefully remove the waste pipe and empty the water into the container below.

Next, disconnect the overflow pipe from the side of the trap.

Remove the lower half of the sink waste. Do this by unscrewing the screws that hold the top of the drain to the strainer. It’s best to reach underneath and hold the bottom of the strainer still whilst you do this.

Now remove the lower half of the waste unit and lift the top of the waste unit out from above.

Use a cloth to thoroughly clean the parts and the area around the hole. Take care as the edge may well be sharp. Carefully clean the surrounding area before replacing washers and reassembling.

To install the replacement strainer, start by placing the thinner, wider rubber washer between the sink and the top part of the strainer.

Then, put the thicker rubber washer and the bottom part of the strainer into position underneath the sink.

Use a screwdriver to tighten the screw and secure in place.

Reconnect the overflow pipe to the waste pipe and then connect to the trap.

Turn your water supply back on by twisting the stopcock anti-clockwise.

Finally, run the tap to check the kitchen sink pipe leak has been resolved. Check the seal periodically for the 24 hours following any repair work.

By following these steps, you can confidently repair a leaking pipe under the sink. We hope this guide helps you get your kitchen running smoothly again.

Several methods for fixing a leaking sink are shown in this guide. But if the problem persists then call in a professional.

If it’s your tap that’s leaking, check out our guide on how to replace a tap washer.

FAQs

A leak under the sink is generally caused by the washers being old, perished or damaged. It can also happen if the compression fittings on the waste pipe become loose over time.

Check all the pipes underneath the sink for drips. To test the drain washers, fit your plug and fill the sink with cold water. Then wait to see if the water level drops.

To fix a leaking sink, you need a screwdriver, a bucket, a wrench, and a cloth. You also need a new kitchen sink waste and overflow kit.