How Can i Tell if my Toilet is Leaking

Look for a trickle around the inside of the toilet bowl. If it is hard to see, you can put some toilet paper around the bowl and look whether it becomes wet or not. Alternatively, you could put a couple of drops of food colouring into the cistern. If it is leaking, you will see the colour dripping down the inside of the bowl. One flush and the food dye will then go harmlessly down the drain.