Leak under kitchen sink: what to do

Finding drips and pools of water under your kitchen sink can be a headache. But don’t put off fixing the issue. Any leak under kitchen sink needs to be resolved efficiently and at the first sign of a problem.

Otherwise a small under the kitchen sink leak might cause bigger issues down the road, leading you to pay out for further costly repairs.

So, what causes these leaks, and more importantly, how can you fix them?

Here’s how to work out why your kitchen sink is leaking underneath – and when to call in the experts.

How to find where a leak is coming from under a sink

Sometimes finding an under the kitchen sink leak can be straightforward. The leak might be obvious and the problem simply a matter of replacing a worn-out washer.

However, there’s a lot going on underneath the kitchen sink. You’ll find an entire network of water pipes generally squeezed into a confined area.

This can often make it tricky to pinpoint a water leak or dripping pipe under sink.

Top tips for finding a leak under the sink:

Clear the cabinet

Empty the under sink cabinet and wipe down all the pipes and walls. You might find the leak straight away.

Lay down kitchen paper

Place a couple of layers of kitchen paper on the cabinet base. Check regularly for any moisture and leave overnight if necessary.

A wet spot will eventually appear. Look above it for the source of the leak and run your hands along the pipework, valves and washers for moisture.

Wrap pipes with toilet paper

If you think the problem is a leaking pipe under sink, then wrap toilet paper around the pipes. It’ll help you pinpoint which pipe is causing the problem.

Fill sinks with water

Next try the sink test. Put the plug in and fill sinks with water. Then let the water drain out and see if you can spot any leaks.

If you’ve got a waste disposal unit try turning that on too. Alternatively, turn on your dishwasher for several minutes, stop it and then drain.

One of these appliances might be the issue.

Test the taps

Check your tap for problems. If yours is fitted with any extra features, try all the different modes and spray patterns.

You might need to replace your tap if it’s old or faulty.

Once you’ve tried all of these methods but still can’t find the source of the leak, it’s a good time to hire a local plumber.

They will have the expertise and specialist equipment to locate the leak and get the problem fixed efficiently first time round.

6 reasons for a leak under kitchen sink

Here are some of the most common causes for a kitchen sink leaking underneath.

1. Kitchen sink drain pipe leaking

Plastic plumbing pipes connected to the sink plug hole are one cause of leaks under the kitchen sink.

This includes connections and fittings connected to those pipes – both at the kitchen sink end and where they go into the waste system.

2. U-bend under sink leaking

U-bends (also known as waste traps) can also be a source of a kitchen sink plumbing leak.

They can become blocked and suffer from wear and tear. Also, the rubber washers at either end of a kitchen sink U-bend might become loose or dislodged and leak water.

3. Leak from hot water supply

The hot water pipe under a kitchen sink is usually located on the left side of the sink. A leaking copper pipe under the sink can be connected to a dedicated, separate hot tap or a kitchen mixer tap.

Sometimes, these pipes and connections can leak due to movement, expansion and contraction, or just general wear and tear.

4. Cold water pipe under sink leaking

The pipework that connects the mains water cold feed can also cause a leak under sinks.

Cold water pipes experience higher pressure than hot water pipes, so in this case, you might come across a sudden leak with lots of water.

Don’t forget to check the stop taps for any leakage or break, too.

5. Kitchen sink overflow pipe leaking

The overflow on a kitchen sink is a small opening that stops the sink from overspilling and flooding if someone accidentally leaves the tap running when the plug is in.

It’s connected around the back of the sink to an overflow pipe that leads down into the drain.

A leaking overflow pipe can be commonly missed, but it’s worth investigating.

6. Leaks from other appliances

Remember that there are often other appliances fitted near the sink.

So it might be that it’s your washing machine or dishwasher that’s leaking and not the sink plumbing connections.

Leak under the kitchen sink when water is turned on

A leak under the kitchen sink that only happens when the water is turned on usually points to a problem with your sink’s plumbing.

Try our tips above to find where a leak is coming from under a sink.

But remember that the leak source might not always be directly above the puddle of water, as water can travel along pipes before dripping down.

Here are a few common sink plumbing problems:

• Loose connections with pipes, connectors and joints
• Damaged seals around sink or tap
• Cracked pipes
• Faulty water supply pipes
• Drain leaks due to a faulty sink strainer or cracked drain pipe

To save you time and get the job done properly, a professional plumber can identify where the water is coming from and take the appropriate steps to fix the leak.

Leak under kitchen sink when water is turned off

Working out the exact cause of a leak when the water is off requires prompt action – and the skills of a professional plumber.

Otherwise, potential water damage and mould growth can arise if left unchecked.

Here are a few reasons why this might be happening:

• Failing seals or gaskets due to wear and tear. Commonly seen around sink flanges, tap base or pipework connections
• Pipe corrosion particularly older metal pipes
• Damaged valves
• High water pressure
• Loose, worn or damaged water supply lines
• Drainage issue such as a blockage

FAQs

What to do when water leaks from under a kitchen sink?

If you notice a water leak under your kitchen sink, try not to panic. The first thing to do is to turn off the water supply under the sink.

Then tighten up any pipework connections and replace washers if they look worn.

If you notice your U-bend (also known as P-trap) is leaking, you should replace it promptly. The water collected in the bend creates a seal that prevents wastewater and sewer gases from entering the home.

We recommend calling an experienced plumber in your area to help you quickly sort out your kitchen sink leaks.

How to fix a leaky pipe under the sink?

If you’ve identified a leaking pipe under sink as the issue, you can try a few things at home.

To temporarily fix a minor leak, wrap it with silicone tape or apply epoxy putty. Then, call a plumber who can fix the leak so it won’t cause any further damage.

Tighten the slip nuts or replace old or cracked rubber gaskets to fix a leaky pipe connection.

How much does it cost to fix a leak under the sink?

Every type of plumbing job requires different materials, skills and labour times. This is why your plumber may charge an hourly rate, a day rate, or quote an overall cost for the job.

The average plumber cost is £50 per hour or £347.50 per day.