The siphon is fitted in the WC cistern and its function is to flush the toilet. It achieves this by lifting and dropping a big seal made of rubber over a hole in the bottom of the WC cistern. It uses the downward water pressure of the full tank to keep its seal. This rubber seal however, can wear or it can develop bubbling, and both could be the reason for a failure, making it leak. It may be that debris is in the cistern. Vauxhall Plumbers can repair a siphon. This kind of debris is usually the remnants of something like a solid freshener that is placed in the cistern. If you think that the siphon is the reason for the leak then:


1). Isolate the water supply and flush the water away. Take off the cistern lid, then, take the top of the siphon off by turning and lifting it away. It may have clips, if so, press them in and remove the siphon.

2). Hold the siphon and visually check the rubber seal on the bottom, looking for any signs of bubbling. If it is poor or damaged then replace it with a new one from your local merchant. Take the whole siphon for identification. The new on will probably need to be ordered so keep the old one until the new one arrives. If the rubber looks ok, then check for debris. Clean out the cistern as a matter of course. A Vauxhall Plumber would carry out this action.

3). Twist the top of the siphon back onto the base, either twist or clip as required. Finally, restore the water supply and visually check that there are no leaks. If for some reason you are not able to replace the seal immediately and the toilet is still leaking lots of water, isolate the WC again until a repair can be done.