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

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

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 with a leaking toilet (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!

Key Takeaway’s:

  1. Check the bolts: The bolts that hold the tank to the bowl may have become loose, causing the leak. Tighten them carefully with a wrench, being careful not to over-tighten them and crack the porcelain.
  2. Check the gasket: The gasket between the tank and the bowl may have deteriorated or shifted out of place, causing the leak. To check this, turn off the water supply to the toilet, flush the toilet to empty the tank, and remove the tank from the bowl. Inspect the gasket for damage and replace it if necessary.
  3. Check the tank-to-bowl nuts: The nuts that secure the tank to the bowl may have become loose or corroded, causing the leak. Tighten or replace these nuts as necessary.
  4. Check the overflow tube: The overflow tube in the tank may be improperly positioned or damaged, causing water to leak out. Make sure the tube is properly positioned and not damaged.
  5. Check the flush valve: The flush valve may be damaged or not sealing properly, causing water to leak from the tank to the bowl. Inspect the flush valve and replace it if necessary.
  6. Check the water level: If the water level in the tank is too high, water may be leaking through the overflow tube. Adjust the water level to the recommended level, typically marked on the inside of the tank.
  7. Check for cracks: The tank or bowl may be cracked, causing the leak. Inspect both the tank and bowl for cracks and replace the damaged part if necessary.
  8. Check the wax ring: The wax ring that seals the toilet to the floor may be worn out or damaged, causing water to leak from the bowl. Inspect the wax ring and replace it if necessary.
  9. Check the water supply line: The water supply line may be damaged or not properly connected, causing water to leak. Inspect the supply line and replace or tighten it as necessary.
  10. Check the fill valve: The fill valve may be malfunctioning or not sealing properly, causing water to continuously flow into the tank and overflow into the bowl. Inspect the fill valve and replace it if necessary.

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 bottom of 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 toilet tank leaking 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 leaking toilet 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 or new gaskets 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 leaky toilet tank 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 flushing 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 water supply valve 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 very eaky toilet. 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 (check the tank bolt pattern for fit), 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 professional 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 toilet base and 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 replacing 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 the toilet tanks your new toilet.

  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.

Troubleshooting leaking toilet tanks can be a frustrating and time-consuming task, but with the following tools and step-by-step instructions, the problem can be repaired. Start small by checking the tank bolt nuts, spud washer, and the old gasket. If the leak occurs from the tank upside, then the spud washer or old gasket may need to be replaced with a new spud washer.

Check the refill tube to ensure it is not too long and causing water to overflow, leading to a leak on the bathroom floor. If the leak persists, turn off the shut-off valve and flush the toilet to empty the tank. Add food coloring to the tank, wait for a few minutes, and check for any signs of the colored water leaking into the bowl.

Inspect the ballcock and the overflow tube to ensure they are not damaged or improperly positioned. If the problem still persists, consider replacing the fill valve with a quarter turn ballcock.

If the task seems daunting or requires specialized hardware, consider seeking assistance from a professional or visiting the hardware store. In the meantime, avoid using the toilet until the leak is repaired to prevent water damage to the bathroom floor or walls. Finally, enjoy a hot shower and the peace of mind that comes with a properly functioning toilet.

Q&A With Guys From the Plumbers Association

Water Heater Hub (WHH): Good morning, everyone, and welcome to this special discussion between us here at Water Heater Hub and representatives from the Plumbers Association. Today, we’re diving into the common but pesky problem of leaky toilets. With me are two expert plumbers, Mr. John Thompson and Ms. Emily Fields. Welcome!

John Thompson (JT): Thank you. It’s a pleasure to be here.

Emily Fields (EF): Thanks for having us.

WHH: Let’s start with a common issue: toilet leaking from the tank. Can you explain why this happens and what some of the unique tricks are to fixing this?

JT: Certainly. Toilet leaking from the tank is often due to a worn-out gasket or faulty shut-off valve. One quick fix is to turn off the water supply, remove the old gasket, and replace it with a new gasket. Reattaching the water supply is essential after this fix.

EF: And don’t forget to check the shut-off valve! Sometimes, simply tightening it can solve the toilet problem.

WHH: Great insights! Now, what about leaks around the toilet bowl? What are your strategies there?

JT: Leaks around the toilet bowl can be due to a faulty wax seal or other connection issues. Replacing the wax seal is often the best course of action.

EF: And, it’s important to make sure the toilet bowl is properly aligned with the flange. Misalignment can cause leaks, so ensure everything is properly positioned.

WHH: Fantastic advice. Now, hot water is a key part of bathroom functionality. Can you talk about the relationship between hot water and leaky toilets? How can hot water be a solution or a problem here?

JT: Well, hot water isn’t usually directly related to leaky toilets, but if there’s a problem with the shut-off valve to the hot water supply, it can lead to other plumbing issues, like leaks.

EF: Right. And in some rare instances, you may need hot water to loosen up old parts when working on a leaky toilet. It’s a tool rather than a problem in this context.

WHH: That’s an interesting point. Finally, do you have any general advice for homeowners dealing with leaky toilets?

JT: Regular inspection is key. Look for signs of wear and tear on the gasket, shut-off valve, and other components.

EF: And don’t hesitate to reattach the water supply if you’ve been working on it or to replace parts like the gasket. Prevention is often cheaper and less stressful than dealing with a major toilet problem.

WHH: Excellent advice. Thank you both for sharing your expertise with us and our listeners.

JT & EF: Thank you!

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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