How to fix a leaking toilet
12 November 2024
Originally published on 6 October 2022. Refreshed with new information and republished on 12 November 2024.
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.
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How to diagnose the cause of your leaking toilet
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.
Time to get to work
Now that you’ve diagnosed the cause of the problem, it’s time to solve it. Here’s some of the most common issues and how to correct them.
Replacing a flush valve
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.
Top tip
You may need a flathead screwdriver to hold the bolt in place as you turn the 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.
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.
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.
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.
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.
Fixing a valve leak
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.
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.
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.
Top tip
Before you start the removal, make sure you’ve removed all the water from the tank. If you remove the fill valve with water still in the system, the water will fall out the hole where the fill valve used to be.
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.
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.
Tightening leaky gaskets
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.
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.
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.
FAQ's
How can you prevent toilet leaks?
To help prevent future leaks, regularly check your toilet for signs of wear and tear and keep up with basic maintenance.
Avoid flushing any foreign objects, as these are a leading cause of clogs that can damage your toilet’s inner workings and lead to future leaks.
What to do when your toilet won't flush?
We have a full guide on what to do when your toilet won't flush.
In conclusion
We hope you found this information useful.
Remember, if you’re still having issues with a managed property, you can contact Places for People.
If you are not a Places for People customer, we do recommend using a reputable website to find a suitable tradesperson such as Checkatrade, TrustMark or Trust a Trader.
In the meantime, why not check out some of our other how-to-guides and insightful blogs?