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Questions about how to fix kitchen faucets leaking under the sink are frequently asked. Even though it might not seem important, a kitchen faucet that leaks at the spout’s base must be fixed.

The Environmental Protection Agency (EPA) estimates that leaking spouts waste approximately 3,000 gallons of water annually in addition to the annoyance of the constant drip.

To save the water and your floor that can be damaged by continuous leaking of water, you have to read this article till the end.

Through this article, you will get to know how to fix a kitchen faucet leaking under sink, its importance, and what its reasons are. In the end, we will try to answer your faucet-related questions.

Also Read: How to clean a pull down kitchen faucet spray head

So let’s dive into the faucet world to resolve your problems.

Why you need to detect faucet leaking under the sink:

Since most people don’t regularly check beneath the sink, leaks under the faucet and sink might be the most difficult to detect. Since the water can only fall to the floor, this leak has the possibility to be one of the most destructive.

This type of leak, if left unattended, can harm your vanity and the floor or seep through the floor, resulting in very expensive damage.

Why is my new kitchen faucet leaking under sink?

Finding the leak’s source requires careful scrutiny; once found, the leak can be stopped by tightening the fittings. The shut-off valve or flexible supply tubing may occasionally need to be changed because they are worn out.

Though less probable, it’s also conceivable that the faucet has to be changed because it is old and worn out. It is conceivable for the tailpieces of a highly ancient faucet to have rusted such tight couplings to flexible supply tubes are no longer feasible.

Pressurized water hose leak:

It is likely a pressured water hose leak if water is consistently dripping from beneath the sink. These leaks are extremely frequent and often happen when the valves get rusted and aged.

These leaks are easily fixed by tightening compression fittings around shutdown valves.

Grab a wrench to tighten the valve, and tighten the compression nut with your hands. 90% of the time, this adjustment should solve your issue; however, occasionally, your sink can leak immediately beneath the tap. Get some adjustable pliers and start working to reach these valves and tighten them up.

Problematic drainage:

If you only notice leaks while the sink is fully loaded with water, the drain is probably the issue’s source. It is necessary to stop all water flow, disassemble the drainage pipe, remove it, clean it, and then restore it, ensuring that everything attached to it is firmly sealed.

To stop water seeping through the connections and valves, compress some plumbing putty around them. If this does not stop the leak in the sink, you might even need to purchase a new drain seal.

Drain leak:

The most frequent type of leak is a drain leak, and it’s relatively simple to find. After turning on the water, empty your sink. This is the root of the issue if you spot any leaks as the water drains.

There’s a good chance you have a blocked drain or that something within the drain is corroded or rusted.
The majority of sinks have a drain that is sealed with plumber’s putty. This putty is beneficial to wear since it stops leaks.

The putty may, however, dry out with the passage of time. Sometimes it was too thin to begin with, and that much water was just too much for it to retain.

Sometimes, the issue is caused by unsecured nuts situated at the intersections of pipes. Before making any other assumptions, make sure these nuts are entirely tight.

Even though loose nuts can result in catastrophic leaks, they are simple to correct. If you don’t have to, don’t squander any money.

Damaged water supply line:

Another frequent type of damage to the kitchen sink is water supply leaks. Try to drain it and let the water run like you would find a drain leak.

If the water isn’t draining, you have this issue but see a puddle forming under the sink. A damaged pipe or joint typically causes water supply leaks.

If the leaks are ongoing, there is another sign of a water supply problem.

Old swage system:

These leaks typically go unnoticed until they wet everything in the storage under the sink. This is due to the connections seldom being in plain sight.

The old and damaged sewage system is responsible for a leak under the kitchen sink. Sewage pipes have an extremely long lifespan.

The majority of us will leave the house before the lines become old enough to deteriorate. However, it is possible.

This leak is typically visible on the wall behind the sink. Pipes are likely to be the cause of any visible water stains.

Unfortunately, this issue may be costly, so you should get assistance from a specialist. Don’t tamper with pipes by yourself since you’ll just do more harm.

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Other possible reasons for a leaky faucet under the sink:   

If the faucet is leaking under the sink. It is frequently necessary to tighten the drain connections if the sink drain opening or the fittings on the P-trap are the leak sources. The drain strainer and tailpiece unit on extremely old sinks could be worn out.  

In this situation, replacing the sink drain fitting will be necessary. The leak may usually be stopped by merely tightening these fittings, though. 

Empty the sink vanity first, then dry everything off completely. Run some water to check where the leak is coming from next.  

Leaks under the sink are most often caused by one of two things: 

  • Loose connections to the water supply. 
  • Connections to the P-trap or sink drain that are loose. 

These leaks can be pretty minor, so if you can’t find the leak right away, place some dry-piece towels on the floor or the base of the vanity, and check back in a few days to see if there are any water stains on the towels. 

Connections you should inspect the water supply lines:

The connections between the supply pipes and the shut-off valves, the connections between the valves and the flexible supply tubes, and the connections between those supply tubes and the tailpieces on the faucet.
Water leaks might be coming from any of these places.

Two water supply connections—one for cold water and one for warm water—typically exist on a kitchen sink.

If your sink has a separately attached sprayer, there may also be the third connection. Any of these connections has the potential to corrode, rust, or break, dripping water.

How to fix the problem:

You will need the following to fix a water leak in your kitchen correctly: 

  • Screwdriver Allen wrench 
  • Pliers with a giant slide joint 

Once you have the necessary equipment, turn off the water supply. Up until they are off, turn both handles.  

Find the water supply valve for your sink, then close it. The cabinet behind the sink should contain the valve. 

To prevent tiny objects from unintentionally falling down the drain, plug the sink’s drain holes. It’s acceptable to use rags, plugs, or a kitchen strainer. 

Disassemble the Faucet

You must disassemble a leaky faucet to repair it. Use your tools to gently and slowly disassemble the valves.

Try to keep track of the bits and pieces as you remove them. Put them out in the order they were taken out, or record the procedure on camera. This will make disassembling and reassembling your faucet much more accessible.

Replace faulty components

Examine each piece after spreading them out. Check for rips, cracks, grit, and dirt. To find out why kitchen faucets leak at the spout, look for damage to the O-ring seal.

Use warm vinegar to clean filthy components and remove ingrained mineral deposits. Put the components in a sandwich bag and fill it with enough white vinegar to cover them thoroughly. Rubberband the bag shut, soak the pieces for an hour, and then rinse with warm water.

Bring damaged components to your neighborhood hardware shop to receive replacements. Never be embarrassed to ask for help to ensure you have the right parts. The easier it is to discover the appropriate sink if you are familiar with its brand and model

Replacing the Faucet

All broken parts have been replaced, and your faucet’s parts are spotlessly clean. It’s time to put your fixture back together now. Use the video or the sink model’s schematic to ensure everything is together correctly.

Reassemble your fixture and tighten everything with the Allen wrench as you go. Leakage results from loose parts. Make sure everything is secure before turning the water back on.

What is the video about how to repair a leaky faucet under the sink:

Obtain backup if the issue persists

Repeat the paper towel test to confirm that the spout base is no longer leaking. For an hour or more, place a paper towel or cloth under the spout. The towel ought to be dry when you get back.

If the paper towel is moist, there could still be a plumbing issue in your pipes or additional problems like water spraying happen.

When to seek professional assistance:

kitchen faucet leaking under sink

Picture credits:                    iStock photos 

Call for assistance if this is the case since water damage is serious business. To find water leaks, qualified plumbers use sophisticated equipment. Allow the professionals to handle the situation so your kitchen sink is fixed permanently.


  • Why is my faucet leaking under the sink? 

Loose water supply connections and leaky p-traps are the primary cause of leaky faucets under the sink. 

  • Why single is the handle kitchen faucet leaking under the base? 

First, bacteria are trapped inside the o-ring and nuts, making them loose. So the loss of nuts of a faucet causes water leakage from the base. 

  • Why does the faucet leak at the base when turned on? 

When the faucet is leaking from the base, the problem is with the fixtures. The faucet has debris accumulated O-rings, and when the seal at the base of the faucet is worn out. Then there will be persistent leaks when the faucet is turned on or when the problem is left untreated then the faucet will leak when it is turned off. 


Even if little leaks and drips aren’t a big deal, you should resolve them. Both your property and your health are vulnerable to severe damage from water. 

It may cause the parquet to rise, spoil the walls or the flooring, or harm the house’s structure.  Leaks may indicate a severe problem with the sewage system under the kitchen sink.  When you leave the leaky faucets under the sink untreated, the issue will cost 10 times as much if you leave them alone.  Don’t be afraid to call a specialist if you are unsure of what is causing the leaks. 

Thomas Louis

Im, Thomas Louis, a passionate faucet and kitchen gadget expert. Im your trusted source for all things related to enhancing your culinary space. With years of dedicated research and a keen eye for innovation, I have established myself as a go-to authority in the world of kitchen fixtures, faucets and gadgets. Whether you're seeking the perfect faucet to complement your kitchen's aesthetic or looking for the latest kitchen gadgets to streamline your cooking experience,As a chief contributor at, I am committed to simplifying your decision-making process when it comes to kitchen upgrades. My insightful blogs provide a wealth of information, from faucet buying guides to gadget reviews that cater to both novice home chefs and seasoned culinary enthusiasts.

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