How to Tell if a Toilet Is Leaking Underneath (And How to Fix It)?

Last update:

A leaky toilet should be pretty easy to notice, right? You can see water coming out of cracks, valves, or joints, so that’s where the leaks come from.

But that’s not the case with a toilet leaking from under the toilet bowl. It forces you to search for the cause of a leaky toilet and then to repair it. In this post, we will show you how to do both.

How to Tell if a Toilet Is Leaking Underneath?

You can tell that the toilet is leaking underneath by awful smell and water around the toilet base.

Water and Dampness Around the Base

One of the first things you’ll see is water flowing out of the bowl. It goes between the toilet and the bathroom flooring, creating puddles all over. If you are lucky, you’ll only find water around the base. If not, there will be dirt and debris, too.

The smell of mold and mildew is also a sign of humidity around the base. That’s when you know your toilet is leaking underneath. The worst thing is that water and dirt keep showing up despite cleaning the toilet frequently.

Foul Odors

Another feature of a leaky toilet is the awful smell coming from underneath. If you notice any kind of odor, don’t wait longer to inspect your toilet. The smell expands when combined with humidity and dirt around the base.

If the entire bathroom is clean, but you still feel awkward smells, it’s a sign of water leaking directly into the base. The water probably goes down the drain, so you can’t see it.

Why Does a Toilet Leak Underneath?

If your toilet is leaking underneath, you should consider a couple of reasons. Only two things can make the toilet leak from down under.

Broken Wax Ring

The first reason is a broken wax seal. It’s responsible for sealing the toilet to the drain, preventing water from spilling on the floor. If it breaks, there will be water around the base. Furthermore, the water level in the toilet keeps dropping

You can also recognize a broken wax seal by a wobbly bowl — the ring keeps the bowl to the ground, but a damaged item can’t hold it tightly enough. It allows the bowl to move in all directions, so you can’t sit still while doing your thing.

Cracks in the Toilet Bowl

Cracks in the bowl are the second cause of toilet leaks. If you spot water on the floor, test it to see any cracks on it. This may be difficult because the cracks are too small to identify, but you’ll notice the bowl is losing water

However, you can find out by putting food coloring or dye in the bowl — if colored water flows out, even if you’re not flushing the toilet, your bowl has cracks. The result is the same because you’ll end up with constant leakages and bad odors.

What to Do if the Toilet Is Leaking Beneath the Bowl?

Now that you know the reasons why your toilet is leaking, you should do something about it. Both problems have a solution, so let’s go through step-by-step instructions here.

Replace the Wax Ring

The first step is replacing the wax ring. It does take some time, but anyone can do it right. The toilet ring is a rubber seal between the porcelain toilet and the floor in a bathroom. You can repair it like this:

Close the water supply by turning the shut-off valve clockwise. If the shut-off valve won’t shut off, spray it with WD-40 penetrating oil — it will lubricate the knob, so you can twist it with ease.

After that, remove the metal hose supplying the toilet tank with water. The hose goes from the water valve to the tank, so you can remove it by turning the compression nut counterclockwise.

The third step is to empty the toilet tank — flush the toilet, and the water will flow out. Now you can unscrew the t-bolts with pliers. It’s a pair of bolts that you can find at the bottom of the tank.

When you unscrew the bolts, you can remove the toilet tank. Unscrewing the toilet bolts is the next step —use pliers to loosen the screws, so you can detach the bowl itself.

Without the bolts, it’s easy to remove the bowl. All it takes is to take the bowl with your hands and place it on the side against the floor. When you look at the bottom of the bowl, you will see the remnants of the old wax ring — use a putty knife to clean it.

Now you can install the new wax ring — put it on the ground to seal the outlet drain of your toilet. After that, you can reinstall the entire structure like this:

  • Put back the bowl and tighten it with a pair of bolts
  • Reinstall the tank by screwing the t-bolts clockwise
  • Reconnect the water hosepipe
  • Open the shut-off valve by turning its knob counterclockwise
  • When the tank fills with water, test the new wax ring by activating the toilet flush

If you don’t see new leaks, your toilet is fully functional again.

Replace the Bowl

If you have a cracked bowl, the only solution is to replace it. The process is similar to changing the wax ring, as you’ll need to repeat a few steps.

Start by closing the water supply valve. When you do it, detach the supply hosepipe and flush the toilet to eliminate water from the tank. If you want to ensure that the tank is empty, you can remove the tank lid and clean it from the inside.

The next task is to unscrew the tank bolts and remove the tank. After that, you should also unscrew the toilet bolts from the toilet base – it will allow you to remove the old bowl. Now you can install a new bowl.

Our advice is to find a high-efficiency bowl with low water consumption. Check different models to see whether they fit your plumbing system. After that, you can pick the best option based on parameters like water consumption and design.

When you install the bowl, you can bring back other elements:

  • Connect the tank
  • Attach the water supply hosepipe
  • Open the water supply line

The Bottom Line

So how to tell if the toilet is leaking underneath? You can tell it by the urine smell and the damp area around the toilet base. These two signs also indicate the cause — your toilet has a broken wax ring or a cracked bowl.

Luckily enough, you can solve both problems with ease. Prepare your tools and get to work — you’ll fix a leaking toilet in a couple of hours!


Can the toilet leak without me knowing?

Yes, the toilet can leak without you knowing. The reason is that toilets sometimes leak directly into the outlet drains, so there are no usual signals such as dirt and dampness on the bathroom floor.

What causes the toilet to leak at its base?

When you see the water leaking at the base, you probably deal with a cracked bowl or a broken ring. These are the two most common problems, but sometimes the cause may also be water condensation due to high humidity.

How do I know where the toilet is leaking from?

You can discover it by inspecting the toilet. Check all parts from the tank – check for leaks in nuts, joints, and tank bolts. You should also check the overflow tube and the fill valve. Sometimes the bowl cracks, so you need to test it as well.

Leave a Comment