UNABLE TO FLUSH MY SYPHONIC TOILET EFFICIENTLY, IT DOES NOT EMPTY THE TANK FULLY, ONLY ABOUT HALF THE WATER COMES OUT ON FLUSHING

PETER FRANCIS, November 2007

After changing the "flap valve", which is just a piece of flat plastic, the toilet was not taking all of the water out of the cistern.Then I changed the washer that stops the air getting into the porcelain U piece when the toilet handle is operated, thus creating the "syphoning" action required. The toilet is now taking all of the water from the cistern.

peter francis, December 2007

Modern syphons have the ability to work like this to save water.
They do it by having a plug which can be removed for water saving mode. Unfortunately older wc pans are designed and need to use more water.
When the plug is removed or falls off, air is introduced into the syphon before the syphoning is complete thereby ending the syphonage process early during a flush.
Look for a hole on the side of the syphon. If you cant replace the missing plug then I can tell you that I have sometimes made a plug using a 10p coin, some silicone sealant and a bit of sticky tape to hold the coin in place until the sealant sets.
If all else fails you may need a new syphon. In this case invest in a modern type which can have its internal parts replaced without having to remove the cistern.
Some really old syphonic toilets have ceramic syphons and extension pieces that can make replacement a bit of a nightmare.

Slugbabydotcom, November 2007