How to fix a blocked toilet

The usual faults with a WC pan are blockages or leaks. A leak from the pan outlet is not difficult to repair, but a cracked pan will have to be replaced.

Clearing a washdown pan

When a washdown bowl is flushed, the 2 streams of water, one from each side of the rim, should flow equally to meet at the front. The water should leave the pan smoothly, not eddying like a whirlpool.

If the cistern is working properly but the bowl fails to clear, something is obstructing either the flush inlet or the pan outlet.

If the flush water rises almost to the pan rim, then ebbs away very slowly, there is probably a blockage in the pan outlet (or possibly in the soil stack or drain into which it discharges).

What you'll need:

  • WC plunger
  • Possibly also flexible drain auger
  • Bucket
  • Mirror
  • Pair of rubber gloves

Simple steps:


1. To clear the pan, take the plunger and push it sharply onto the bottom of the pan to cover the outlet. Then pump the handle up and down 2 or 3 times.

drain auger

2. If this does not clear the pan, use a flexible drain auger to probe the outlet and trap.

3. If the blockage persists, check and clear the underground drain.

4. Flush the cistern to check that water is entering the pan properly, with streams from each side of the rim flowing equally to meet at the front.

5. If the flow into the pan is poor or uneven, use a mirror to examine the flushing rim. Probe the rim with your fingers for flakes of limescale or debris from the cistern that may be obstructing the flush water.

Clearing a siphonic pan

Blockages are more common in siphonic pans because of the double trap and the delicate pressure reducing pipe seal (also known as the atomiser seal). Do not use a plunger on a blocked siphonic pan because this can dislodge the seal.

A blockage can usually be cleared with an auger or by pouring several buckets of warm water into the pan. But if, after clearing the blockage, the water still rises in the pan as it is flushed, renew the seal.

What you'll need:

  • Screwdriver
  • Adjustable spanner
  • Container for bailing or a tube for siphoning
  • Silicone grease
  • Pressure reducing pipe seal

Simple steps:

1. Remove the cistern and locate the pipe protruding from the bottom of the siphon.

2. Remove the rubber mushroom-shaped seal and fit a replacement. Lubricate the new seal with silicone grease so that it will slide down the pipe.

3. Refit the cistern and test the flush. The water should be removed from the bowl with a sucking noise before the clean water comes in from the rim of the bowl.