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How to fix a leaking toilet

Man Fixing Toilet

Whether water is leaking into the bowl or onto the floor, a leaking toilet is always an inconvenience you could do without. Luckily, we’re on hand! To help you diagnose the problem and walk you through the repair, we’ve created this handy guide to toilet DIY.

How to diagnose the cause?

Turn off your water supply 

Firstly, shut off the isolation valve. Typically found at the rear of the toilet, this valve is sometimes found elsewhere on your toilet unit. Once you’ve found the valve, turn it clockwise as far as you can.

Mark the water level in the tank

Mark the highest point where the water in the back of the tank reaches, this will help you discover if the water rises or falls over time.

Colour your water and wait 10 minutes

Dying your water can help you see whether the water in your tank is leaking into the bowl. Dye tablets or food colouring can help you do this.  To dye your water, add one dye table or ten drops of food colouring to your water tank.

Wait at least 10 minutes to ensure that tank water has completely changed colour, then continue with the following steps: 

Has the water changed colour?

If the water in your bowl has any trace of dye, your tank water is leaking. This means the cause of your leak is a faulty flush valve and It’ll need replacing.

Check the water level in your tank

If you notice that the water has risen, there’s an issue with your fill valve. However, if the water level has gone down, there’s a leak in the flush valve.

If your water level has gone up, check if there’s any water in your overflow tube. This would mean that the fill valve is leaking and overflowing the water tank.

Check the floor for leaking water

If the dyed water has seeped out from the bottom of your tank, it means you've got a leaking gasket. If the water comes out of the body of the tank, the tank itself might be cracked. In this is the case, the tanks will have to be replaced.

Replacing a flush valve

1. Turn off and flush

Turn off the water supply and flush away any remaining water in the tank. If you can’t flush the toilet, you can use a cup to remove the water from the back of the system.

Toilet Flush

2. Remove the supply tube nuts

The tank is attached to the wall by the supply tube and then attached to the toilet bowl by two bolts under the tank. Use an adjustable wrench to loosen and remove these nuts.

Toilet Tube Nuts

3. Lift the tank off the bowl

Place the tank upside down next to the toilet bowl on a stable surface. To avoid water spillage, put some towels down and place the tank on top of them. This positioning will also give you access to the flush valve on the bottom of the tank.

Man Lifting Toilet Tank

4. Unscrew the locknut and remove the valve

You can find the locknut in the middle of the tank that holds the flush valve in place. Unscrewed the locknut and push on the flush valve to pop it out. For the best results, used a plumber’s wrench to unscrew the locknut.

Man Removing Locknut And Valve

5. Replace the old flush valve

To install the new flush valve, push it down against the tank opening. Remember to follow the manufacturer’s instructions to ensure you’ve installed the new valve properly.

Replacing Flush Valve

6. Tighten the locknut with a monkey wrench

Reattach any parts of the flush valve that you disconnected when you removed the old one. Be sure to replace the gasket over the locknut as well.

Tighten Locknut

7. Place the tank back on the toilet and tighten the bolts

Tighten the nuts that fix the tank to the supply tube and the toilet bowl that were loosened during the process. Once reattached, you can turn the water supply back on and refill the tank.

Once everything is back in place, flush the tank to ensure the leak has fully gone. if it hasn’t, check to make sure the leak isn’t coming from somewhere else.

If water is still leaking into the toilet bowl, go back and ensure you’ve fully tightened the bolts attached to the flash valve.

Man Tightening Toliet Bolts

Fixing a valve leak

1. Turn off the water supply and remove the water from the tank

Turn the water supply valve on the back of the toilet clockwise, then remove the water by flushing or using a cup to remove the water.

Man Tuning Off Water Supply

2. Disconnect the water supply tube

Located underneath the fill valve below the tank, turn the water supply tube anticlockwise with a wrench to disconnect it.

Depending on your toilet design, the supply tube will either be a long, rigid pipe or a short tube connected to the water supply shutoff valve.

Water Supply Tube

3. Unscrew the locknut attached to the fill valve

The locknut can be found underneath the tank that holds the fill valve in place, it’s usually found next to the supply tube. Use a small wrench or pliers to loosen and remove the locknut.

Locknut Attached To Fill Valve

4. Remove the old fill valve through the top of the tank

Take the lid off the top of the tank and pull the old valve upwards to remove it.

Removing Old Fill Valve

5. Install the new fill valve in the tank, following the instructions

Place the new fill valve in the spot where the old one was and screw the locknut onto the bottom of it. Be sure to attach the refill tube to the side of the fill valve and place it over the overflow tube in the tank.

Remember to read the manufacturer’s instructions, they will include guidelines for how high the fill valve’s float needs to be.

Installing New Fill Valve

6. Reattach the water supply tube and turn on the water

Once the water supply has been turned back on, flush the toilet to test the new fill valve. If it fills correctly and doesn’t overflow, the repair is complete.

If you’re still experiencing problems with water leaks, your toilet may have a more serious issue. Contact Places for People to arrange a plumbing appointment.


Water Supply Tube

Tightening leaky gaskets

1. Turn off the water and empty the tank

Start by turning the water supply off by rotating the valve behind the toilet clockwise. Once the water’s been turned off, flush the toilet to empty the tank.

Top tip: you can also use a cup to remove the water out of the tank.

Toilet Flush

2. Find the bolts that connect the tank to the bowl

These are two or three bolt heads surrounding the flapper in the bottom of the toilet tank. You’ll recognised the bolts by the rubber washers found underneath them.

Man Connecting Tank To Bowl

3. Tighten up the bolts with an adjustable wrench and screwdriver

Use a flathead screwdriver to hold the bolts in place, then take an adjustable wrench and turn the bolts underneath the tank clockwise to tighten them.

Man Fixing Toilet

4. Refill the tank and check for leaks

Turn the water supply back on and allow the tank to refill. Wait a few minutes, then check for seepage. If there’s no more leaks, the gasket has been fixed. If there’s still leakage, the washer under the bolts will need to be replaced.

Man Checking For Leaks