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Finding And Fixing A Leak Under The Bathroom Floor: A How-To Guide

Note: This post may contain affiliate links. This means that at no cost to you, we may receive a small commission for made purchases.

A leak under the bathroom floor can be subtle and go unnoticed for quite some time, which can prove quite dangerous a problem. Within a few days, you could be stepping into a pool of water as soon as you step out of the bath.

You should want to sort it out yourself as the problem is not going to go away and no one wants to be wasting water. Finding the leak can be one thing yet fixing it is quite another. 

In this guide, we will look at how to identify a leak under the bathroom floor and how to fix it. We will also look at how you can identify other bathroom leaks.

Finding And Fixing A Leak Under The Bathroom Floor: A How-To Guide

How To Identify A Leak Under Your Bathroom Floor

A leak under the bathroom floor can either be obvious or can prove difficult to spot depending on the source of the leak. All that time when the leak is occurring and you cannot identify it could amount to more money to eventually fix it.

If you do find that your bathroom floor has a puddle that has not been caused by someone leaving the bath or shower then quickly look up.

Should you see water droplets or water stains then the water could have come from the ceiling, if not then it may well be a leak under the bathroom floor.

Check The Plumbing

The first thing you should check is the plumbing going under your sink for any telltale signs of leaking. Areas around your toilet and bath may be important too so check them thoroughly for any droplets of water.

If all seems to be dry then try to listen carefully and if you can hear a hissing sound then that may indicate a leaking pipe which could lead you to the leak itself.

There are further plumbing areas outside your bathroom that could result in a leak which include the kitchen sink, ceiling pipes, and drain. 

Inspect The Floor

Take a look at the pooling water and this should give you an idea of how promptly you need to find where it is coming from. A small amount of water would be difficult to find the source yet if you can see a bulge on the floor then this could lead you right to the leak’s source. 

Check Underneath The Bathroom

A leak under the bathroom floor can be shown by what lies underneath. Say that the bathroom is on the second floor, then check the room directly under as a leak under the bathroom floor would show some signs. Perhaps a water stain or water droplets forming on the ceiling. 

Poorly Installed Toilet

A likely culprit for a leak under the bathroom floor is if the toilet was poorly installed. This has a lot to do with the measurements that are taken between the toilet and the wall as any gap could cause a leak.

The issue may mean re-installing the toilet which can take time and cost money but it could fix the leak.

Turn Off The Water Meter

Another way to check where the leak is coming from is by turning off the water meter. In order to turn off the water meter, you effectively have to turn off every single source of water. That includes the faucets so the water running through your pipes is limited.

Make a quick check of the water meter and make a note of the level, then return a few hours later. 

If the level on the water meter stays the same then there may not be a leak and it could just be a spillage. However, if the water meter indicates that water is still being used then there could well be a leak and it could be coming from an outside source.

This could be rainfall that is still seeping into the house through some structural issue which would likely be a costly problem to fix.

How To Fix A Leak Under The Bathroom Floor

Once you have successfully identified the leak being under the bathroom floor, you will want to fix it quickly before the problem gets worse. This can mean either taking apart the ceiling from the room below or taking apart the bathroom floor itself.

Typically, it is easier to solve the problem from underneath, and it can be more expensive to replace any bathroom tiles that you currently have. 

Install Bathroom Floor Fitters

Occasionally, a leak under the bathroom floor can be inexpensive to fix. Should the issue be caused by cracked tiles then you can install some bathroom floor fitters. As long as the cracks underneath them are sealed then that could be the end of it. 

Fix The Leaking Pipe

If you have located the specific pipe that is leaking then focus on turning off the water that goes there. Fixing that one pipe could solve the problem though you would need a professional plumber as a temporary solution will only last so long.

A water leak can cause serious damage to your home’s structure so fix it once and for all.

Identify The Outside Water Source

Stopping the leak could well mean stopping the source of all the water that comes into the house. Yet if the pipes are not found to be the problem with a first-floor bathroom then the problem may be harder to solve as the water could be coming in from outside.

These sources of the leak could be from badly sealed foundations, holes or cracks in the foundation floor, or a crack in your home’s exterior. Finding a crack in your home’s exterior may mean using a plug to close it until you hire a professional to fix it but issues with the foundation floor and foundations are harder to spot.

Seal The Crack

If the leak under the bathroom floor is from a badly sealed foundation or issues with the foundation floor then you could use some cement.

However, you should consult with a construction expert as this could be another temporary solution if there is substantial structural damage. This is particularly serious as cracks in the foundations can always get bigger.

How To Identify A Bathroom Leak

How To Identify A Bathroom Leak

If you know how to solve a leak under the bathroom floor then a more general leak in the bathroom should be easier to solve. While you can expect a bathroom leak occasionally, especially in an old house, identifying it quickly will save you a lot of hassle.

There are several ways of identifying a leak in your bathroom and some are more obvious than others. 

Damp Patches/Puddles

The most obvious sign of a leak under the bathroom floor is the unexpected sight of some water. Sure, you can rely on some being on the floor after someone has just stepped out of the shower or a bath yet a puddle of water in the middle of the day should be a rare occurrence.

Especially if the water is pooling where you should least expect it to, specifically in your cabinets or surrounding the base of the shower or bath. The damp patches, or simply some dampness, that can appear on the floor or all the way to the ceiling are another hint of a leak. 

Peeling Wallpaper

If you do have wallpaper in your bathroom and you notice it beginning to peel then this could be another sign of a leak. This would be due to the damp patch that lies underneath the wallpaper causing it to peel from the wall.

It could be down to time and a failed adhesive yet if you check and feel the dampness then you may have a leak.

Tiling Problems

Like the peeling wallpaper, if you have tiles on your bathroom wall and you see water cascading down them, this should be worrying. Loose or broken tiles are a concern anyway yet if water is coming through then it is likely that the damage is already done.

Tile leaks can be costly to repair and hopefully only require the tiles and grout to be replaced but occasionally it means new backing. 


A lot of bathrooms are going to suffer from mold as the environment is damp and humid which are the perfect conditions for mold to develop.

However, if a damp patch arises from a leak then mold can grow on top. If this occurs in an area that you would expect to be dry then you may well have a leak. 

Odd Smells

Sometimes you can smell a problem before seeing it with your own eyes. This can be the case for mold in your bathroom as well as the damp and mildew that can develop.

If you can smell an earthy, dank odor, like you would in the basement, then there may be a leak in the bathroom. You could try to mask the bad odor with some air freshener but that is only hiding the bigger problem as the leak is only going to get worse.

Leaking Noises

If you can hear a leak, this is a surefire sign of one before you need to see the pooling water. That drip, drip, drip should be investigated promptly as the leak will continue to cause damage in places that you cannot even see yet.

Leaking noises can occur in the night when no one is using the bathroom. Not only can that prove to be really annoying but the noise can signify the increasing cost of fixing the problem.

Unsecured Faucets

Faucets that move around and wobble can often signal a leak originating from the sink rim. They may drip from time to time but that is not the issue as the newfound movement would indicate water that is coming up from beneath the base of the faucet itself.

Thankfully, this kind of leak should be simple to solve by tightening the faucet base below the sink. As long as the water fails to re-emerge, you can reapply the caulk. 

Final Thoughts

Leaks under the bathroom floor can be difficult to solve as it can take time to find out the source of the water. More time spent identifying the issue and the source of the water can mean a higher cost of eventually solving the problem.

When in doubt, consult with a plumber to find out where the leak is originating from and they may also be able to solve it. If the leak is from structural damage to the house then get in contact with a construction expert as this is a problem you would not be advised to sort out yourself.

Frequently Asked Questions

Why Are Leaks In The Bathroom Considered Dangerous?

If you have any pools of water in your bathroom then that can be considered a hazard. Not only can someone slip and strike their head against the sink or bath, but the water can also cause a short circuit due to the electrical devices.

There is the risk of electric shock by touching the electrified water and with the connecting wires, a power shortage can be caused if there is sufficient liquid.

If the standing water is left alone it can cause health issues from the growth of mildew and mold as well as cause damage to the drywall and warp any wood.

Can Water Leak Through A Bathroom Floor?

Yes, quite easily in fact and you would see water droplets on the ceiling from the room below. The water can come through tiles that have damaged grouting or silicon.

These files can become loose from the water and then fall off. Water from a leak can also pool behind walls then drip through the floor without you even noticing.

author avatar
Anthony Barnes
Anthony Barnes is the founder of Water Heater Hub and a second-generation plumber by profession. Before developing Water Heater Hub, Anthony Barnes was a full-time plumber, and he has undertaken a wide variety of projects over the decades. As a second-generation plumber, it was easy for Anthony to get used to the technicalities of all from a tender age


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