Toilet Leaking Between Tank And Bowl? Why And How To Fix It

Toilet Leaking Between Tank And Bowl? Why And How To Fix It

Anthony Barnes

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Toilets are complicated little things, with lots of different components, and sometimes when they start to break, or leak, it can be hard to figure out exactly where the fault is, what the fault is, or how to fix it.

And since your toilet is something pretty essential that you or members of your family are using multiple times throughout the day, it’s pretty important that you figure out the problem and fix it as soon as possible. Otherwise, you’re going to find yourself in an uncomfortable situation.

One of the main issues you can have is the toilet leaking (see also ‘How To Replace A Leaking Toilet Tank To Bowl Gasket’) from between the tank and the bowl. But what causes this? And how do you fix it when it does happen?

Let’s find out the answer!

Why Does Your Toilet Leak Between The Tank And The Bowl?

So, a toilet tank is placed at the top of the bowl so that gravity enables the water to be pushed down to the tank when you pull the lever and flush the toilet. Usually, your tank is bolted in with around 2 to 3 bolts which then have a metal and a rubber washer behind them to ensure it stays in place.

Now when you have a leak here there are two possibilities. Either there is a leak from the tank to the bowl, or between the tank and the bowl. If it’s the first then your toilet flapper is most likely warped or bent. This is a nice easy fix, as the flapper just needs to be replaced.

However, if your leak is coming from between the bowl, then there are a few possibilities. Your tank-to-bowl gasket is likely to be the main offender, but you could also have loose toilet tank bolts or worn bolt washers.

It’s quite easy to tell what’s at fault in this situation. If the leak is consistent then it’s probably the bolts and washers that are responsible. However, if your leak only seems to happen when you have flushed the toilet, it’s the gasket.

Unlike the broken flapper, a leak between the bowl and tank is going to take a bit more effort to solve. This is because you’re going to need to replace the gasket, and potentially the bolts and washers too. It’s always worth just trying to tighten up the existing bolts first to see if that solves the problem. If it doesn’t then you will have to replace them.

The gasket is a piece of rubber that is installed on the outside of the flush valve. The purpose of it is to keep the seal watertight so that when the water leaves the tank and enters the bowl it doesn’t leak. If the gasket is worn out, this seal breaks and the water can leak through.

The bolts’ role is to compress the gasket and also create a watertight seal. If these are loose there will be no seal and therefore a leak. As hard water can often corrode these bolts, they have to be replaced as corroded bolts are certain to leak.

Rubber washers can become overly worn, and when this happens water can slowly seep through the bolts and pool at the bottom of the toilet bowl.

Now, you can choose to just replace the one item that is broken, however, I would personally recommend that you change all three together, as when one goes the others usually follow shortly after.

The parts are also not massively expensive and usually come as part of a set. So it makes sense to replace them all together and save yourself a job in the long run.

How To Fix The Leak

How To Fix The Leak

So now that you know why your toilet is leaking, it’s time to try and fix this leak. Now there are 3 different ways you can solve this problem so we will go through each option.

  • Tighten The Loose Tank Bolts
  • Replace The Toilet Tank Bowl
  • Replace The Tank To Bowl Gasket

If you replace the bowl you should really always replace the gasket too as so I’m going to combine there into one point.

Tightening Loose Tank Bolts

Here’s an easy to follow step-by-step guide to tightening your loose tank bolts.

  1. Using both hands, attempt to rock the tank sideways.
  2. If there’s movement, the bolts are loose, and you have identified the issue of the leak.
  3. Locate the bolts/nuts underneath the bowl. They should be located on either side of the bowl.
  4. Using an adjustable wrench alternate between the bolts until both are tight. If you do not alternate the bowl will not be level so ensure that you do this.
  5. Always tighten bolts carefully and gently because if they are too tight they will crack the porcelain and then you will need to replace the whole thing – and that can be expensive.

If you try to rock the tank and notice it doesn’t move much, then the bolts are probably fine. In this case, you’re going to want to move on to this second method. Before you do though, make sure you’ve checked which tank to bowl gasket will fit your toilet as they can come in more than one size.

Replace The Tank To Bowl Gasket/Tank Bolts

Be warned, this is going to take a little time and effort as it’s quite a lengthy process but fear not because it is actually a fairly simple procedure.

If you don’t think it’s possible you can do it yourself you could always call a plumber, but honestly, I’d try and give it a go yourself as your plumber is going to charge you a fair bit to sort it themselves.

So for all you do-it-yourselfers here’s a step-by-step guide to get the job done.

Step One: Drain The Tank

So the first thing you’ll need to do is drain your tank of all the water. This is fairly easy to do.

  1. Turn off the water to the toilet. Locate the shut-off valve and turn it clockwise/pull it out depending on the type of valve you have.
  2. Flush hard, holding the lever down. This will get the maximum amount of water possible out of the tank.
  3. Take off the toilet tank lid. Move it to a safe space where it’s unlikely to get damaged.
  4. Soak up any remaining water. It’s easiest with a sponge.

Step Two: Remove The Tank

Next, you’ll want to remove the tank from the toilet you’ll do this by following these steps.

  1. Disconnect the hose from the tank. I’d suggest trying to loosen the coupling with your fingers before you immediately reach for your wrench. It’s also in your best interest to keep a small bowl beside you as the hose may still have water in it. Use the bowl to collect this water.
  2. Using your fingers, feel around the toilet tank bolt nuts under the bowl. There should be two of these.
  3. Loosen the nuts with your wrench.
  4. If you struggle to loosen the nuts, take a screwdriver and hold them from inside the tank while still loosening the nut from the other side with the wrench. Get someone to help you with this if you continue to struggle.
  5. Corroded bolts will need to be cut with a hacksaw blade. You’ll need just the blade as the whole thing won’t fit.
  6. Lift away the tank and place it in a safe space where it won’t break.

Step Three: Replace The Gasket And Bolts

Now you need to replace your tank to bowl gasket and as well as the tank bolts.

  1. Hold down on the tank and slide the gasket out and discard it.
  2. With your wrench and screwdriver disconnect the bolts.
  3. Replace with the new bolts and washers. Be super careful arranging the washers- the rubber washer should touch the toilet but the metal ones should never come into contact with it.
  4. Push the washers on the bolts on the outside of the tank and hand-screw the nuts until they’re tight. Then tighten them further with your screwdriver and wrench.
  5. Once the bolts are in place, you can set the gasket into place too. Make sure that it fully covers the flash vale nut.

Step Four: Install The Tank

You’ve made it to the penultimate step so well done! All that’s left to do now is install your new toilet tank.

  1. Lift the toilet tank (see also article on how to remove rusted bolts from a toilet tank) and direct the bolts through the holes at the top of the bowl. Make sure you do so carefully.
  2. Secure the rubber washer and the metal washer, and screw in the remaining nuts at either end of the bolt under the bowl.
  3. Use a wrench and alternatingly tighten the two bolts ensuring that the tank is level.
  4. Be careful to not tighten the bolts so hard that it cracks the toilet.

Step Five: Test The Toilet

And you’ve done it! All that’s left to do is check that everything has been installed correctly.

  1. Ensure everything is in order. If the flapper has moved, reposition it back into place.
  2. Reconnect the hose back to the tank – this only needs to be tightened by hand.
  3. Reopen the toilet shut off the valve and wait for the tank to fill back up with water.
  4. Keep an eye out for any leaks between your tank and bowl for about 5 minutes.
  5. Flush the toilet and spend another 5 minutes checking for leaks.
  6. If there are no leaks, place the lid back on and pat yourself on the back for a job well done.

Final Thoughts

I know that fixing this problem can seem like a lengthy process, and just from looking at all the steps you may be tempted to just call a plumber instead, but I promise that it’s nowhere near as scary and complicated as it looks.

Try it out for yourself and see!

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By 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