Diagnosing a toilet that won't flush

If your toilet won't flush there's no need for it to drive you round the bend. Follow our easy advice to get your reluctant loo back on track.

Float ball

  1. Lift the cistern lid and check that it is full of water. If it isn't, check the float ball (the big plastic ball in the cistern which controls the level of water in the tank).
  2. Make sure the float isn't touching the side of the tank and stopping it from rising. If it is, gently bend the flat rod to move it away from the side of the tank.
  3. At the same time, check that the float rod isn't broken and that the float itself isn't leaking. If so, it'll need replacing.

Flapper valve

This can be found right at the bottom of the tank and lifts open to let the water through into the toilet bowl.

Yank this up to let the water flow out. If this allows water through then the problem is with the connection from the handle to this flapper valve – more than likely the connection between the lift arm and lift chain is broken and needs to be adjusted or replaced.


Is the handle too loose or too tight? Try flushing and adjust the mounting nut if needed. It may also have become stiff with limescale, so give it a clean.


This runs from the lift arm down to the bottom of the tank where it lifts the rubbery flapper valve.

  1. Is the chain bent or broken? If so bend it back or replace it.
  2. It should have about half an inch of slack, so adjust it by hooking the chain onto a different hole on the handle to get the right tension to sufficiently lift the flapper valve.

If after performing these simple checks your toilet is still not flushing, give a professional plumber a call.

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