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Water Leaking from Under the Bathtub: Possible Causes and Solutions

Water in bathtub

The bathroom, with all its plumbing fixtures is most susceptible to leaks, with the bathtub being at the forefront of it all. Most of the time, people don’t even realise the tub is leaking until mould develops or they see water leaking from the ceiling under the bathroom. If you find yourself in this situation, you’ve come to the right place.

Also, if you have been living in a property that’s quite old and wonder how to locate the source of the leak, then read along and learn the causes and possible solutions for water leaking from under the bathtub.

Why is the bathtub leaking from underneath?

Bathtub leaks shouldn’t be ignored even if they start out small. In time they will get larger and may lead to flooding. You already know that mould can also develop, so that’s another reason not to postpone the repair. So, why is your bathtub leaking underneath?

  • The bathtub is cracked – The first and most obvious cause; however, it’s not always that easily noticeable. Some cracks can be as fine as a hairline yet still cause trouble. The easiest way to check is to fill the tub with water and turn off the tap. Then look closely at the water for any areas that seem to be sucked down. If you do notice a crack, you can repair it by purchasing a repair kit. There are two kinds on the market: those for surface repair and those for internal repairs. Both have self-explanatory instructions, so they should be easy to implement.
  • Bathtub taps are leaking – The most common problem that everybody ignores because the water goes into the tub and doesn’t cause mould to develop. However, the constant dripping may start to corrode the area it hits. Usually, the rubber washers inside the taps are the reason for the leak. There you can fix the dripping tap by yourself, provided you have a screwdriver and an adjustable wrench. However, it’s possible that the washers are not the problem, but rather the taps themselves, in which case you need to get in touch with a professional.
  • Issues with the grout – It’s completely possible that the leak is not coming from the pipework or drainage system, but from the shrinkage of grout. Indeed, the grout can shrink around the tiles, which are always hit by water. This issue is easy to fix. You need to regrout the tiles with a mixture of silicone caulking and grout. The equal parts of the two will create a new moisture barrier.
  • Bath overflow pipe leaking – This pipe is located at the back of the bathtub. The most common reason is the gasket between the actual overflow pipe and the tub; it dries up and cracks with age or due to lack of moisture. It’s possible to change it on your own, but you will need some initial preparation. More on that down below…

Check also: How to Check for Bathroom Leaks – A Homeowner Guide

Can a leaking bathtub be repaired and how?

Yes, in some cases, you can repair the bathtub leak on your own, depending on the nature of the problem. It’s very important to pinpoint the source of the leak so you can fix it properly and not damage something that’s already in good condition. The following two are the most common reasons why your bathtub leaks, and you can fix them on your own.

How to repair water leaking from bathtub drain

If you live in a two-storey home and you notice water leaking from the ceiling under the bathtub, then you need to replace the bathtub drain. This repair is easy and cheap to carry out, but you will need several items:

  • Tub drain remover wrench.
  • A flathead screwdriver.
  • Plumber’s putty.
  • A new drain if the old one is broken. It’s possible that it’s not, and instead, the seal needs replacing.
  • Vacuum cleaner.

And this is how to repair water leaking from the bathtub drain:

  1. Place the tub wrench in the drain. The tool has two ends for different drain sizes; choose the one that fits snugly.
  2. Put the screwdriver in the little hole in the tool for extra leverage and turn the tool left to loosen the drain.
  3. Remove the drain.
  4. Scrape off the old plumber’s putty from the hole using the flathead screwdriver. Afterwards, vacuum the area to remove even the tiniest of pieces.
  5. Remove the gasket from between the bathtub and the drain spout. If it’s in good shape, clean it and put it back in. If it’s cracked, replace it.
  6. Put the clean or new gasket inside the hole in the tub and be careful so that it won’t fall in.
  7. Get a little ball of plumber’s putty and roll it, so it resembles a fat piece of spaghetti.
  8. Roll the putty around the drain and do it gently.
  9. Screw the drain back into the hole. Start by hand until you can’t anymore. Then put the tub drain wrench and tighten it fully.
  10. Remove the excess putty once the drain squeezes it out.
  11. Let the putty dry for about 24 hours.
  12. Close the drain and run some water over it. This is to test for any potential leaks. If you see no bubbles, then you’re good to go.

Fixing a leaking bathtub overflow pipe

The overflow tube is a flooding prevention feature, and each tub and sink has it. Its purpose is not to let the water rise above a certain level by channelling it back down into the drain pipes if it reaches that level. In time, the fittings become loose, and some of the water can start to spill out and drip beneath the tub.

Here is how to check if indeed the overflow pipe is the cause of the leak under your bathtub.

  • Find your access wall panel. It’s usually on the backside of the plumbing wall of your bathtub or shower.
  • Remove the access wall panel.
  • Look for water dripping from the plumbing. If there is non, look inside to see if water is pooling behind the wall. Puddles are signs that you likely have leaks around the drain pipe or supply line.
  • Run the shower and splash water on the tub taps.
  • Check behind the access panel again. If there’s no water there, then it’s likely that your overflow pipe is the problem.

This is how to fix the tub overflow drain:

  1. Unscrew the overflow cover plate. There may be a bracket underneath it, so unscrew that as well.
  2. Pull out the overflow drain assembly along with the plug.
  3. Inspect the assembly and the gasket. It is possible parts of the overflow drain are loose, corroded or clogged; however, usually, the culprit an old, dry gasket.
  4. Remove the old gasket from the pipe flange. You might be able to do it by hand, but if it’s too hard, you might have to use needle-nose pliers.
  5. Clean the exposed flange with rubbing alcohol.
  6. Insert a new gasket in the old one’s place.
  7. Position the gasket in such a way that the thicker side is at the bottom. Work it into place around the overflow assembly opening. It needs to be secure around the flange.
  8. Reattach the overflow cover plate.


Learn also: How to Unclog Your Bathtub Drain – Some Quick and Easy Methods

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

Prices for plumbing services vary and the specifics of the repair often play a major role. The average costs of plumbing services, in general, can vary between £40 to £80 per hour and £160 to £300 per day. Sometimes you pay one sum for the first hour and a smaller sum for each subsequent hour. Still, take those numbers with a huge grain of salt and instead call professionals for an accurate quote, corresponding to your circumstances.

The prices can differ because of the following factors:

  • Your location – The further away you are, the more fuel will be used.
  • Time of the year – If your tub springs a leak during the busy seasons, you will be charged more and possibly have to wait.
  • Urgency – If the leak is small, you can wait until plumbers are available. On the other hand, emergency plumbing repairs cost more and for a reason.
  • The scale of the job – a leaking bathtub will not cost you an arm or leg, however, you never know what kind of problems will come up after the inspection has been carried out.
  • Duration – each company estimates how long the job will take. Small repairs might take one to two hours. Large repairs will take and cost more.


  • You might have a leak under your bathtub because of cracks, old washers in the taps, or old gaskets in the drains.
  • Always fix the leak as soon as you spot it because otherwise, it will become more serious as time goes on.
  • Repair the bathtub drain by replacing the old gasket with a new one and with a fresh plumber’s putty.
  • Repair the overflow pipe by replacing the old gasket with a new one and position it in such a way that the thicker side is at the bottom.

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Water Leaking from Under the Bathtub: Possible Causes and Solutions

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