On Sat, 03 Jan 2009 12:54:28 +0000, MM wrote:

Anyway, I just had a brainwave (in the last couple of hours). I
swapped the top part from the downstairs loo with the bathroom one. No
dribbling!!! I've switched the water back on again and flushed a
couple of times. Still no dribbling!!! So it is definitely the rubber
seal on the end of the plunger thingy.

PS to my last post: The seal on the top part from the downstairs loo
has some blue gunk on the contact surface, which I left in place.
Anyone know what this blue gunk is? It must have been smeared on when
the unit was being assembled when the house was built in 2004.
Whatever it is, it has mostly stayed in place despite numerous
flushings over four years. NB: This gunk is definitely man-made, i.e.
not some chemical reaction. It definitely looks as if the plumber
smeared some "stuff" on the seal before assembling the syphon inside
the cistern.

MM