My Toilet Leaks At The Base When My Tub Is Draining? (Possible Causes & Fixes)

Matthew Mountain
by Matthew Mountain

Leaks are distinctly problematic for homeowners, as leaks can occur in numerous places around a home. What’s causing a leak is not always apparent, but there are a few common things to look out for. If you can pinpoint the exact cause and location of a leak, then addressing it will be easier.

If there is a leak at the base of the toilet, it’s probably because the mainline to the sewer is clogged. A clog can be broken up using a snake. Loose bolts and faulty wax rings can also lead to leaks. If it’s the bolts, tightening them should remedy the situation. If it’s the wax ring, replacement will most likely stop the leak.

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When You Discover a Leak

Take Safety Precautions

When dealing with a leak, it’s best to take preemptive measures to ensure your safety. The water from a leak can be teeming with harmful bacteria, and such is why it’s important to gear up before attempting to handle one on your own.

Wear clothes you don’t mind parting with. You might have to throw your clothes out after the problem has been fixed, especially if the leak is a particularly messy one.

Gloves and a mask are also recommended. Gloves will prevent wastewater and bacteria from making contact with your skin, while a mask will ensure your lungs aren’t exposed to harmful gasses and particles.

But if the leak is a bad one—and this is obvious—it’s best to call a professional plumber straight away. Large leaks can be dangerous for a variety of reasons. A professional will know how to protect themselves, as well as those in your home, from anything harmful that’s related to the leak.

Stop Using Your Appliances Immediately

If there’s a leak somewhere in your house, it’s probably because a pipe or drain is clogged. When water can’t get through the proper channel (pipes), it backs up and builds pressure until an exit is found—or made. If the leak is in the bathroom, you’ll need to absolutely avoid using any electrical appliances.

Is the Main Sewer Line the Problem?

In modern homes, toilets, bathtubs, and sinks all have a connection to the main sewer line. A clog in the main sewer line will affect all plumbing-related fixtures in the home, and addressing a clog of this nature isn’t usually something a homeowner can do on their own.

In most cases, the municipality in which you live will be responsible for clearing the block. It could also be that your local water company handles these issues, so get on the phone with them if you suspect there’s a clog in the mainline.

Common Reasons for Toilet Leaks

There’s a Clog in the Drain Line

A clogged drain line is the most common explanation for a toilet that’s leaking at its base. When the toilet is used, the water and waste in the bowl is flushed down the drain. But if the sewer line is clogged, obviously the water and waste can’t pass through.

This leads to the water exiting from anywhere else it can. If water exits from your toilet’s base, it’s likely because the toilet is the closest fixture to the sewer line. A leak can also spring from a sink, shower, tub, etc.

The Toilet Has a Compromised Wax Ring

A compromised wax ring at the base of the toilet can also be what’s causing the leak. If this is the case, the toilet will need to be moved so the wax ring can be replaced.

The wax ring holds the toilet in place, but it also serves as a barrier between the toilet and the drain line. The seal this ring forms ensures that water and waste don’t leak out during the transfer from toilet bowl to drain line.

A compromised wax ring isn’t the only thing that can cause a leak. If the ring is loose, the same result is likely.

You can replace a wax ring on your own, but hiring a plumber is the option most homeowners go with in this situation. Removing the toilet on your own can be hard labor, as toilets are generally very heavy.

Your Toilet Is Loose

Since toilets are bolted to the floor, it’s possible that the connection is not as secure as it should be. Moreover, uncaulked toilets tend to be more prone to unwanted movement.

The bolts which hold the toilet in place are covered with tee bolts. Tee bolts can become loose, especially when too much pressure (weight) is applied to the toilet. They also wear over time.

Fixing this problem is simple. All you’ll need to tighten the tee bolts is a wrench. Turn the tee bolts clockwise until they’re secured over the bolts. Don’t over-tighten. Afterward, flush the toilet a few times to make sure the leak is gone.

Alternative Ways of Fixing a Toilet Leak

Use a Plunger

If you know there’s a clog, this should be option number one. Although a leak at the base of the toilet is most likely because of a clogged drain pipe, plunging is still worth a try before attempting another method.

Use a Drain Snake

This tool will be able to break up a clog easily. Drain snakes are also called drain augers, and one can use this tool to push accumulated material so it breaks up.

Drain snakes are available in different sizes, but most drain snakes are between six and fifty feet long. If you suspect the clog is deep down the drain, you’ll need a long snake.

To start, insert the drain snake into the toilet. Extend the drain snake until it collides with the clog, and then begin cranking the drain snake.

After a while, pull it back out to clean away any debris that has accumulated on the device. Repeat this process as many times as you need to.

Approach the Clog From Somewhere Else

If the first two methods were unsuccessful, you might need to unclog the drain using what’s known as a drain cleanout. This opening will give you easier access to the clog.

First, you will need to locate the drain cleanout. Once you do, assess its position in relation to where the clog is. You’ll need a wrench to open the drain cleanout.

The drain cleanout can let out a lot of wastewater when opened, so you should be ready for this. Again, take precautionary measures beforehand.

Grab the snake again and stick it through the drain cleanout. Snaking from this location should be easier and more effective. Afterward, flush the toilet and check for leaks.

Other Signs You Have a Sewer Line Clog

In addition to a leak at the base of the toilet, there are other signs which indicate a main sewer clog. It’s good to know what these are, as identifying a clog early will ensure it doesn’t damage your plumbing fixtures.

Overflowing Bathtub/Shower Drain

If you flush the toilet and then notice bubbling in the bathtub/shower drain, you most likely have a clog somewhere. Again, water that is unable to drain properly into the sewer line will present somewhere else in the house.

Overflowing Sink

If you use the sink and you notice the toilet water start to rise, this is another indication of a clog. Bubbles in the toilet will also indicate a clog, as water and air are entering the toilet with nowhere else to go.

Overflowing Washer

The principle is the same here. If using the washer causes water to appear inside the toilet bowl, bathtub, or sink, there’s a good chance there’s a clog in the main sewer line.

A Really Bad Smell

This one is pretty self-explanatory. If there is a clog in the sewer line, you may notice the unmistakably foul smell of sewer gas. Immediate action should be taken to break up the clog in the sewer line, as the smell will be unbearable.

Related Questions

How much does it cost to fix a toilet leak?

As of 2021, the average cost of fixing a toilet leak is around $150. Of course the rate you pay depends on who you hire and how long it takes them to complete the job. If the leak is a severe one, the cost could be anywhere between $400 and $500.

What if I have a septic water system?

Fix the problem immediately. One-fourth of homes in the United States use septic systems, and more than four billion gallons of wastewater enters the ground each day. This poses an incredible threat to our drinking water.

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Final Note

While highly unpleasant and distressing, toilet leaks and bathtub overflows are most commonly due to issues with the main sewer line. Diagnosing the problem can sometimes be harder than finding a solution to the problem, and such is why most homeowners don’t tackle these problems alone. A local plumber will dislodge the clog for you, ensuring you can use your plumbing fixtures as intended.

Matthew Mountain
Matthew Mountain

Matt loves everything DIY. He has been learning and practicing different trades since he was a kid, and he's often the first one called when a friend or family member needs a helping hand at home. Matt loves to work with wood and stone, and landscaping is by far his most favorite pastime.

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