Informational Guide

How To Fix Kitchen Sink Leak

Here’s how to fix kitchen sink leaks the easy way, to help prevent long-term damage to your cabinets & belongings below.

by Ian Haynes

Your kitchen sink is one of the most used fixtures in your home, but unfortunately, even the best brands of kitchen sinks can develop leaks.  

These leaks in your home can, at best, be inconvenient, but if left unchecked, they can become a massive problem, so it's important to fix the leak as quickly as possible. This guide will help explain why these leaks happen and how to fix a kitchen sink leak quickly.  

Before we get into how to fix a leaking kitchen sink, let's talk about what causes the leak in the first place. It’s important to understand what the common causes are, as this might influence how you go about fixing it. Here's a quick breakdown:  

Faucet Leak 

A leaky kitchen faucet is one of the easier issues to spot, and often water will pool at the top of the sink when you turn the faucet on. You might also notice the faucet dripping, or even see a leak underneath the sink. Generally, this is caused by a worn-out gasket or potentially a failed or damaged washer. Both issues are fairly easy and inexpensive to fix.  

Drain Leak 

One of the more serious issues you may have to deal with is a leaking drain. You can usually check the drain by plugging the sink, filling it, and then taking the plug out and watching underneath the sink. If it starts leaking at this point, you may have a drain issue.

Drain leaks can be a result of improper installation or if there's not enough plumbers putty to seal it up. It could also just be because the drain is old and needs to be replaced. The good news is that if your drain is plumbed correctly, it's unlikely to be an issue. The bad news is that a drain leak could mean you need professional help.  

Clogged P-Trap 

Your P-trap is the curved section of pipe directly underneath your sink, which is used to stop potentially harmful gases from traveling back up into your kitchen. Debris and food waste can build up over time and cause a blockage which may eventually cause a leak. 

With metal sinks, corrosion can also cause a leak from the P-trap. It's sometimes difficult to spot a leak coming from your P-trap, and you'll need to check all the connections and pipes under your sink to be sure.  

How To Fix Kitchen Sink Leak

Loose Water Supply Connection 

Water is generally supplied to your sink through two separate pipes, though some sinks have a third water source if they have a built-in sprayer. A leak in these water lines can be caused by a failed gasket, but it can also be caused by corrosion in some cases. 

If you notice a continuous leak, it's most likely a loose water supply connection, but thankfully it's not too difficult to fix.  

Corroded Valve Seat 

Your valve seat sits between the spout and the faucet and connects into the compression mechanism in the sink. Over time, corrosion can cause a leak to start from here, which is normally easy to spot but can be challenging to fix. You may need to call in a plumber if you think your valve seat is corroded.  

Worn-out Washers 

Your washer gets pressed into your valve seat every time you use your faucet, and the friction caused can damage the washer. Over time it will become worn out, and this can lead to leaking. This is one of the most common causes of a leaking sink, so it's worth checking this first.  

Damaged O-Ring 

The O-ring is a small disk that is the part of the sink that helps hold the faucet in place. Over time the O-ring can become worn or loose, and this can cause a leak from your handle.

This usually means you need to replace the O-ring, but that's not normally too challenging.   

How To Repair A Leaking Kitchen Sink

How To Check for Leaks Under A Sink 

It’s important to carry out a thorough check of your sink regularly to see if there are any leaks or issues to be aware of because it isn’t always obvious. You should start by inspecting all the pipes and connections above and below your sink, using a flashlight so you can see it all clearly.

You should then run some cold water through your system and check all your pipes and connections again for any visible leaks or pooling of water.  

If you can't see anything, then keep the faucet on and take a cloth or piece of kitchen roll and run it over your kitchen sink pipes. If any moisture is absorbed, it means that water is leaking from the pipes, and there may be an issue you need to fix.    


How To Fix Drain Leaks Underneath Your Sink?  

A leak from your drain can be quite serious, and you'll need to take action to solve the issue. If your drain is leaking, then you’ll usually need to replace at least some of the parts, and we’ve provided a step-by-step guide below to fix your drain from underneath. 

However, before you start, you should make sure you have these tools: 

1. Clean The Area 

Start by removing all the items around your sink. That means completely clearing the kitchen cupboard and making sure you have as much access as possible.  

2. Turn Off The Water Supply 

This isn’t technically essential because there shouldn’t be any water flowing into your drain, but it’s usually a good idea to turn off your water supply just to be sure.  

3. Disconnect The Drain From The Sink 

Using a plumber’s wrench, twist the slip nut counter-clockwise until it comes off. A lot of modern PVC pipes can just be removed by hand, so you may not even need the wrench.  

4. Remove The Locking Nut  

On the strainer underneath your sink, there should be a very large locking nut. You should use your wrench to loosen the nut until you can remove the drainpipe from the strainer. This will allow you to replace it. 

5. Scrape Off The Plumber’s Putty 

Now you've removed the strainer; you can scrape off the plumber’s putty from the sink. This is important so you can install a new drain, but make sure you don't scratch the underside of your sink. 

6. Prepare Your New Strainer 

Your new strainer will have a rubber gasket, washer, and strainer basket. Separate out these parts so you can install them in the next few steps. 

7. Put Plumbers Putty On The Strainer 

Roll some plumbers putty out and loop it around the edge of the top of the strainer (the part that will sit just above the lip of the sink). Make sure it covers evenly to prevent any future leaks.  

8. Install The Strainer  

Place the new strainer in the sink and push it down gently, so it stays in place. Reattach the rubber gasket and the washer underneath and then screw on the nut. Use your wrench to tighten it so your strainer doesn't spin and is securely in place.  

9. Reconnect The Drainpipe 

You can now reattach your drainpipe and tighten the locking nut back in place. Remove any excess plumber's putty and test the whole drain, looking for any leaks. If it's all working fine, then your job is done.  

If you follow the instructions above, it should only take 5-10 minutes to replace the strainer and get your sink working properly again.  


Plumber's Tips For A Leak-Free Kitchen Sink 

Preventative measures are always best, and there are some things you can do, as a homeowner, to stop you ever having to repair your kitchen sink: 

  • Check Your Pipes Routinely 
    You should make an effort to check your pipes regularly, following the steps outlined further up in this article. It may not seem like a good use of your time, particularly if you don't think there's a problem, but early detection is what stops a leak from turning into a disaster. Make sure you work up a schedule, so you're checking on them at least once a month.  
  • Watch What You Put Down Your Sink 
    Leaks are often caused by inappropriate materials being poured down the sink. You should avoid putting oils, fats, or non-degradable items down your sink as they can cause blockages which in turn can lead to leaks. If you have a garbage disposal attached to your sink, then you can put food waste down there but avoid putting any hard materials in there, which can damage your disposal and your sink.  
  • Wrap Your Pipes 
    One of the leading causes of leaks is damaged pipes, and your kitchen sink pipes can be knocked about as you use the cupboard underneath the sink. Wrapping your pipes helps to provide an extra layer of protection and can even help protect against the cold in the winter months (freezing pipes can be a nightmare). This will help improve the longevity of your pipes and prevent them from leaking.  
Kitchen Sink Leaking Underneath

People Also Ask (FAQs)

Can you use plumber’s putty to stop a leak? 

Plumbers putty is used as a sealant to prevent leaks. You can use it to stop leaks in a specific area, but you will need to find the root cause (which is sometimes the plumber's putty itself).  

When should you not use plumbers’ putty? 

Plumber’s putty is used as a sealant and not an adhesive. Don’t use plumber’s putty just to hold a pipe or component in place.  

What do plumbers use to seal pipes? 

There are many different sealants available. Plumber’s putty is commonly used, but you can also use tape or thread.  

How much will a plumber charge to fix a leaky kitchen drain? 

Repairing a leaky drain can cost anywhere from $500 to $1500, depending on your location and the type of drain you have. Therefore properly maintaining and protecting your kitchen sink drain can save you a lot of money.   


Conclusion

Your kitchen sink is essential, but you will likely have to deal with a leak at some point. The key to fixing the leak is working out what the problem is, so you know which parts might need to be replaced.

Hopefully, this article has helped you understand the common causes and how you fix a kitchen sink leak yourself.  

Ian Haynes is an expert writer who has successfully deployed over 500 plumbing pages and other related content. He has an excellent understanding of home plumbing issues and translates his experiences via Plumbing Lab so readers can have a better understanding of common household problems. Outside of his work, Ian likes exploring Brooklyn with his Labrador.

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