Your Complete Guide To Fixing A Leaking Toilet.

Hey guys Jack here, so you got a leaking toilet and you want to have a lash at doing it yourself… then this post is just for you. In this step by step guide, I’m going to run through everything you need to know regarding how to fix a leaking toilet.

What your going to learn in this guide is to work out where the leak is and which section you need to fix.

As a disclaimer, I am a licensed plumber and my methods may be different to others.

There are a few people class as a leaking toilet and I will go over all the areas that I know that cause a toilet to leak.

  1. Leaking from the tank consistently
  2. Only leaks when flushed

How to fix a leaking toilet.

When the toilet leaks from the tank we still have to break it down a few more steps to see if it’s the inlet float valve, the seating rubber or from under the bottom depending on the type of toilet system you have.

The steps are much the same but in this example where going to use just a standard toilet bowl with the cistern tank mounted on the wall.

Scenario 1

To check if its the float valve, pull the lid of the tank off and check the height of the water level. All toilet cisterns have an overflow pipe built into the tank for this reason.

If the float valve fails the excess waters run into the overflow pipe and down into the toilet bowl.

99% of the overflow pipe is located in the center of the tank.


If water is pouring down that tube then the float valve is faulty and needs replacing.

See below to see how to replace an inlet valve

Scenario 2

If the water level is below the overflow outlet then it must be the seating rubber that sits on the bottom of the flush valve.

The flush valve is what operates when pushing the flush button or lever allowing the water to flow from the tank to the bowl.

If the seal is worn, perished it will allow water to past, wasting water into the bowl.

If your not sure if the seal is worn and you know the float valve is good, try this trick.

Let the toilet sit for few minutes if just been flushed to fill and settle. Then place a piece of toilet paper to the back of the bowl just above the water line but not in the water.

If after a short time the toilet paper is wet, and the water level is below the overflow height, its the seating washer rubber.

Scenario 3

Both the toilet float valve and the seating rubber are all good and it leaks only when toilet is flushed.

If it leaks where the pipe connects to the toilet bowl then it’s the pan cone rubber or key seal rubber. Same but different.

Thye both do the same job just one sits inside the housing on the toilet bowl where the other goes on the outside of the housing. See below.


The only part that varies in size is the pipe that connects the two. Will either be 40mm or 50mm flush pipe. Most newer suites are all 50mm just some sold school toilets still have 40mm rubbers.

If the water leaks from around the pipe where it joins to the tank, then it will be the flush pipe o-ring.

That is just an o-ring that slides over the pipe and screws onto the toilet cistern tank. See this image below.


That is pretty much the 3 main reasons and what to look for if you’ve got a leaking toilet.

How To Replace Toilet Fill Valve

As you know me here’s my no fluff stuff easy step by step guide for you to know how to replace toilet fill valve or an inlet valve on a bottom entry toilet cistern.

You will need a new float inlet valve. Everyone has there own preferences and here in Australia, for years I was always a Fluidmaster user but nowadays for the simple and easy installation and adjustments I love Reeces performa inlet valves.

Replace toilet fill valve on a leaking toilet is just one of those easy to do jobs with just a couple of hand tools that most people have in there home.

You can replace the rubbers in any toilet float valve but the problem is that it’s still old. For the time and around 20 bucks just get a new one

Spending all its life submerged in water things can and do perish over time. The simplest thing is to replace the complete valve and have it trouble-free years to come.

Replacing the toilet fill valve.

What you will need is an adjustable spanner that will open up to the size of the nut that holds the valve in place.

Towel to clean up any excess water that spills onto the floor.

New toilet flush valve.

New flexible water hose optional

Check the toilet stop tap for isolation. If the water doesn’t completely turn off at the stop tap you may need to turn the water mains off.

Next Step On How To Replace the toilet float valve.

Now first of all. Make sure the water is turned off.

Check the toilet stop tap for isolation making sure there is no water entering into the tank. Nothing worse taken the hose off and water are still leaking out of it and onto the floor or bucket you have.

If it is not isolating the water completely now you may need to replace this isolation tap or turn the water off at the mains of the property. Once you have all that organized let’s move on to getting the job done.

Drain all the water that is in the toilet tank. As much as you can drain less will spill on the floor so give it one more flush. Once it’s all drained remove the water inlet pipe or hose.

This could be a copper pipe or a flexible hose.

This is the hose that connects the toilet valve to the water supply.

Either way its needs to disconnect before you can remove the float valve.

This pipe or hose will be under the toilet cistern tank.

Once the pipe is removed off the valve there is a plastic nut that holds the toilet fill valve to the tank.

Remove the plastic nut that holds the valve in place.

This nut is situated underneath the tank just above where you took the pipe off.

Now remove that toilet flush valve by undoing the plastic nut and lifting the float out up through were top.

Of course, you will have to take the lid of the tank first.

Installing a new toilet float valve

Remove the new float valve from the box and install rubber grommet over the threaded end.

Make sure that the flat side of the rubber is facing the flange on the float valve.

Place the new water float valve into the same position as the old one. When in position screw the locking nut from underneath back on and tighten.

Take care when you tightening up the toilet valve that no moving parts rub against the sides of the tank and fouling its operation.

Once the bottom entry float valve is in position install the water pipe back onto the float valve where the thread is.

When installing the water pipe always connect the pipe to the valve end first.

What I mean by that is the float valve thread is plastic and the stop tap is metal. It is much easier to cross-thread plastic than steel. Just a friendly tip there.

Test and commission 

Once the valve is installed turn on the water so we can set the toilet flush level. Fill up the cistern tank and check for any leaks.

 If there are no leaks and you are happy.

Flush the toilet a couple of times and then you may have to carry out a toilet float valve adjustment to adjust the water to the toilet flush level.

Most toilet cisterns have marks on the inside that gives you a water level height.

Normal adjustment is around 9 liters for a full flush and 4.5 for a half flush.

Newer toilet suites use less water and are more environmentally friendly so saving water at 6 liters for a full flush and 3 liters for a half flush.

How To Replace The Seating Washer On Your Leaking Toilet

Now that you have determined that it’s the seating washer. Now we will go through the steps to replacing it.

The only thing you will need for this job is a seating rubber.

They do slightly vary depending on the brand of toilet you have.

I will be using my old trusty Caroma cistern that is mounted on the shitter in the shed.

So I will need a Caroma seating rubber or flush seal, whatever you wanna call it.

Use the orange ones and not the cheap imitation black seals, ok.

How To Replace Toilet Cistern Seating Washer.

First off, turn the water off to the toilet cistern. Either via the stop tap or mains isolation. On the bottom of the cistern there will be a hose or metal pipe. Chase that back and that will be connected to the water line and should have a tap there, where you can turn the water off.

Once you got the water off, remove the lid off the tank to where you will expose the internal parts of the toilet cistern.

You can drain the tank by pressing the button down or you can wait until we remove the flushing valve assembly. It doesn’t matter when as it can’t damage anything.

Now that you got the lid off and all open, as said this guide is for a Caroma mid-level cistern. The mechanism in these just clip in and out. Some have a twist-lock system and their the main two types.

Different brands have different washers and its the size and thickness.

Carefully undo the mechanism housing from its location mounts and remove from cistern.

Make sure you have a towel or rag to catch the drips, as the  seating washer on the bottom of the outlet that you just removed will be perished and will leave black marks everywhere if not caught.

Once removed from the cistern and is dried off, remove the old seating washer.

To remove the old washer depending on the style of cistern outlet valve there maybe a plastic dome nut that holds the washer on.

Others are just a simple pull off and on style. Either way which ever style valve you have when installing the new seating washer, make sure that its centre to the base it sits on.

Before you install the cistern outlet valve back into the cistern make sure you check the seat is ok.

The seat is where the seating washer sits and is located at the bottom of the cistern. If the seat is not smooth the washer wont seal onto the seat and will cause the new washer to leak.

Install the mechanism back into it original location making sure all the clips are fully located into position. Turn the water on and let the cistern fill up.

After the cistern has filled check the water height making sure its still at correct level and you didn’t bump it when removing or installing the outlet.

When you are happy with the water height put the lid back onto the cistern making sure it clips back into place. Now flush the toilet and check for operation.

Flush the toilet a few times to seat the washer into place then check making sure you have fixed your leaking toilet.

How To Install A New Toilet Pan Cone Rubber

This section is going to show you how easy it is to install a new pan cone rubber.

You will need a new pan cone rubber. They come in two different sizes and they are 50mm and 40mm.

The only part that varies in size is the part that fits on the pipe. The rubber that connects to the toilet bowl are all the same size.

If you’re not sure what size you need, just rip the old one off and take it in with you when grabbing the new one.

The video below goes through the steps that I do and there is no set way really.

This is how easy it is. Now for those who know me you already know I don’t drag it out and fluff it up.

  1. Turn the water off if you like and drain the tank.
  2. Remove the nut from where it attaches to the toilet tank and remove it from the housing.
  3. Pull the rubber off from the back of the toilet bowl.
  4. Remove the rubber from the flush pipe and push on the new one.
  5. Locate the pipe into the back of the bowl but don’t roll the rubber on yet.
  6. Attach the pipe to the tanks and tighten up then roll the rubber over on the bowl.
  7. Test it for any leaks and jobs done.

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