Leak on a toilet: possible causes how to repair the flush?

A leak on a toilet is a problem that should be resolved quickly or risk seeing your water bill increase. Moreover, a water leak, even small, can in the long run cause significant damage to your home or to your neighbours.

Several possible causes

The leak can be visible in several places: between the toilet seat and the ground, at the level of the water inlet or even in the bowl itself.

At ground level, either the tank is no longer airtight, or the evacuation seal is altered.

At the level of the water inlet, limestone or the dilapidated state of the tap may be the cause.

Finally, at the level of the bowl itself, it is the flush that poses a problem. Repairing it can be quite simple.

Toilet flush: two causes of leaks

When the flush has a leak problem, two manifestations are identifiable:

  • the tank constantly fills up and the water does not stop,
  • the tank fills up periodically, without anyone having activated the flush.

In the latter case, the cause is the same as when the water no longer stops. It’s just that the leak is very small, resulting in a progressive emptying of the tank which only fills below a certain level.

Composition of a flush

Your toilet flush consists of a water tank which is filled by a filling mechanism. The height of the water in the tank is controlled by a float. It activates a rod stopping the water supply when the tank is filled. An overflow system prevents any overflow from the tank in the event of a defective float, resulting in unlimited flow in the bowl.

At the base of the cistern there is an element called a “bell”, a valve (and possibly a rubber ball) which rises when the flush is activated, in order to allow the rapid evacuation of water from the cistern into the bowl.

The mechanism of a flush is therefore generally simple, but it can be easily disrupted under the effect of wear and/or limescale and thus lead to leaks.

Intervene on the float

A misadjusted float is the most common cause of toilet bowl leaks. It no longer rises sufficiently, even if the tank is full. The water then flows continuously into the bowl through the overflow system.

If the float no longer goes up, it may be punctured. If it fills with water, it can no longer perform its function, so it must be changed.

But the limestone could also have accumulated on the stem along which it rises. What you need to do then is:

  • close the water inlet tap,
  • flush the toilet to empty the tank,
  • open the tank after unscrewing the flush action system,
  • clean the rod to remove limescale, either by rubbing it with the abrasive side of a dishwashing sponge, or by using white vinegar or lemon.

On this occasion, you may find that the rod is deformed. In this case, you will take the opportunity to straighten it to ensure the correct movement of the float over the entire length.

Once this is done, you can reopen the water inlet valve and observe if the float rises to the correct height, stopping the water supply. If the leak is resolved, close the tank and screw the flushing device back on.

Change the mechanism of the flush

If the leak persists, the bell or the valve are at fault. Their movements seize up, either because of limestone or because of the aging of the mechanism.

You then proceed as above to empty the tank.

Then you remove the mechanism by rotating it a quarter turn.

You unscrew the screws located under the seat to remove the tank. You empty the water that may remain at the bottom. You put the tank on a flat surface to easily access the bottom. You remove the seal and remove the remaining parts.

Before installing the new mechanism, take the opportunity to change the outer seal, the one between the seat and the tank (the inner seal is included in the new mechanism you are installing).

Remember to take your old mechanism with you when you go to the store to buy a new one: you will be more sure of choosing the right one!

If the leak persists after having intervened on your flush, you must deepen your search for the cause and turn to the other causes presented at the beginning of the article.

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