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Why Toilet Leaking Into Basement [5 Reasons & Solutions]

A slow-growing damp area on your basement ceiling indicates that the upper-floor toilet is leaking. It’s natural to be worried when you notice water in your basement.

You must determine what is causing the leak. Because if you don’t solve the problem right away, you risk further ruining the basement.

So, why is your toilet leaking into basement? 

A toilet leak is frequently caused by the fixture itself. A toilet has a lot of parts that work together to keep it running smoothly. There are seals, flush valves, wax rings, and pipes for the water supply and drainage system. Any flaw in these components can make the toilet leak into the basement.

You’ll need to learn more than that in order to fix the leak. That’s why we’ve broken down each cause as well as its solution. Stick with us for further details!

Why is Your Toilet Leaking into the Basement

A toilet that leaks into the basement is a big problem. You could be facing a massive crisis. Water damage can jeopardize your home’s foundation, and it can also cause serious damage to the basement.

There are numerous connection points, moving elements, and seals that may cause your toilet to leak. The following are some of the more common causes of water leakage

Reason 1: Damaged Toilet

It’s possible that the source of the leak is the toilet itself. Pools of water on the floor might be caused by breaks in the tank or bowl. This can later leak into your basement.

Look at the back of your commode to check whether the base is cracked or not. It’s most likely a crack if water only spills after flushing. It’s possible that the crack is in the porcelain or the connecting pipe. The sealant holding the pipe pieces together could also be worn off.

Reason 2: Faulty Wax Ring

If you notice water pooling at the foot of your toilet then a faulty wax ring is behind this. Your commode is connected to a drain pipe. This pipe carries sewage water from the commode to your sewage line.

A toilet flange along with a wax seal connects the commode to this pipe. The toilet flange is normally screwed down at four places. And then a wax ring is used to create a watertight barrier between the flange and the floor.

This wax ring could sometimes develop a crack or dry out. And cause water pooling at your toilet. Water can also pool at the toilet base if the flange is higher than the floor.

Reason 3: Damaged Bolts & Gaskets

The toilet bowl and the tank are held together by two bolts and rubber gaskets. These rubber gaskets can deteriorate and fall apart over time if they are not maintained well.

It could also loosen the bolts, causing the water from the tank to leak into the bowl. This excess water can easily cause leakage into the basement.

At the same time, this water has the potential to rust metal bolts. With time the bolts will easily fall apart. 

Reason 4: Faulty Drain Pipes & Water Supply Lines

Damaged drain pipes and defective water supply lines can also cause a toilet to leak into the basement.

Your toilet is connected to the water supply by a hose. This is connected in place by bolts and a gasket. This supply line usually comes from the sidewall or the floor. Any pipe, whether inlet or outlet, can have a leak.

There’s also a shut-off valve on this line. Although these shut-off valves are of different sizes. They are still quite vulnerable to leakage. But you can use these brands’ shut-off valves for better results.

Here are some products recommended for you that you can check out:

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Reason 5: Damaged Floor

Sometimes the damaged floor is behind the leakage. Check the flooring around the toilet flange with a screwdriver to ensure it is solid. If the wood is soft, it is rotten.

If the leak has been there for some time, the rot will have progressed to the subfloor and floor. 

These are all potential causes of a leaking toilet. Now that you know why the toilet is leaking, let’s look at how to fix it.

How to Fix the Leaking Toilet

Sometimes it only takes a few tools to fix the leakage. Always seek expert advice if you are unsure about being able to fix it. Now let’s look at the steps for fixing the problem-

Step 1: Turn Off Water Supply

Turn the water supply valve off. It will be behind your toilet. And it will be connected to a hose that will either come from the floor or the wall. Depending on your water supply, you may also have to close the main valve.

Step 2: Clear Out the Water

Clear out the toilet as best you can. Flush the toilet to move water all the way from the tank into your waste pipe. 

Holding the handle down will keep the water flowing until the pressure is too low. Put on gloves and soak up any remaining water with a sponge or rag. 

Step 3: Repair Depending on the Leak

You need to follow the instruction below and repair depending on the leakage source

For Damaged Bolts & Gaskets

Unscrew the tank bolts that are at the bottom of the tank. Remove the tank from the bowl and the gasket from underneath the tank.

Fit the new gasket onto the knob on the bottom of the tank. To seat the gasket, place the tank on top of the bowl and press down.

Replace the bolt washers on the tank with new ones. Place the bolts through the washers and into the slots at the tank’s bottom. Screw the bolts tightly onto the tank. 

For Faulty Drain Pipes & Water Supply Lines

This type of leak can often be remedied by changing the connectors. But if the water supply is leaking, remove the broken pipe and replace it with new connections. There should be no cracks or dents in the water supply lines.

For Faulty Wax Ring

You’ll need a wrench, disposable gloves, and a scrapper for this job. Remove the bolts that hold the toilet to the floor first. Lift the toilet carefully, maintaining it parallel to the floor, and set it on its side.

Put the disposable gloves on and start scraping. Scrape the old wax ring from the toilet bowl’s base and the floor’s flange.

The new wax ring should then be placed on top of the flange. Put the toilet back into its original spot and bolt it to the floor.

For Damaged Toilet

If the porcelain on the toilet is damaged, it must be replaced. You could use putty or mortar to make a quick repair. Unfortunately, this is not a long-term solution.

If the issue is with the connecting pipe, you’ll almost certainly need to contact a skilled plumber.

Both of these problems have more complicated solutions. For these tasks, it is best to use a professional.

For a Damaged Floor

If there is only moderate rot, flange support will be strong enough to prevent further problems. It should be installed around the flooring.

Drill into the adjoining stonework and attach the support to the solid flooring just outside of the toilet. This should be enough to secure the floor.

Step 4: Put the Toilet Back On

Carefully reinstall the toilet once the issue has been resolved. Reconnect the water supply. Flush the toilet when the tank is filled to see whether it works. Check for any further leaks after that.

How Much Does It Cost to Repair a Leaking Toilet

The cost of the repairs will be entirely determined by the source of the leak. Bolts are inexpensive to replace, costing between $1 and $2. You may get wax sealing for as little as $10.

Toilet flanges are slightly more expensive than wax seals, ranging from $20 to $40.

If the entire toilet must be replaced, the repair will be around $200 to $400.If you replace the toilet, you should also repair the seal. Moving the toilet from the floor will save you money in the future.

Protecting Your Basement from Future Water Damage

It’s quite natural for extra water to settle at the lowest place. This is why your basement is the most vulnerable to water pooling.

You can take preventive measures beforehand. So your basement is protected from this unwanted water damage.

Water can easily get into any cracked structure and damage it. If you see any cracks, seal them as soon as you can.

Make sure that your pipes, walls, and ceilings are properly insulated. Insulation will keep harmful moisture out from the exterior or from the upper floors.

You can use waterproof paints and coatings on your walls.  These sealants act as an additional barrier to keep out harmful moisture. Primers for old plaster walls can also be a protective barrier.


How long does a wax ring on a toilet last?

A wax seal will usually last the lifespan of the toilet, which is 20 or 30 years. The wax ring, on the other hand, may need to be renewed from time to time.

What kind of damage can a leaking toilet cause?

A leaking toilet can rapidly become an expensive problem. A tiny leak might cost several hundred dollars and hundreds of gallons of water. According to Survey, a  leaking toilet can lose an additional 22 gallons of water each day.

Is water damage caused by a toilet leak covered by homeowners’ insurance?

Homeowners’ insurance will contribute to covering damage caused by plumbing leaks. Only if the leak was unexpected and accidental. On the other hand, water damage caused by negligence is not covered by homeowner’s insurance.

End Words

That was all we had to say about your toilet leaking into basement. We hope this has helped you understand the problem.

Contact a professional if the problem persists after troubleshooting.

Good luck!