I have a cheap plastic hiddern cistern. After flushing the cistern leaks by dribbling down the flush pipe. This is the excess water that hasn't made it down the flush pipe.

The flush pipe connects to the cistern by just being fed up inside the flush chamber, with only a rubber seal and tightening nut around the flush pipe to stop any water leaking out. This seems like a pretty poor arrangement to me, as anyone looking at this would expect it to leak at some point. Also the rubber seal doesn't seem thick enough to seal up the gap between the outside of the flush pipe and the wall of the cistern flush.

What i want to know is if this is a typical arrangement, or has this been botched at installation? Also how can i fix this properly so there are no more leaks in the future?

Any help is much appreciated :)
Thanks

Mr D, June 2010

yes i see what your talking about with the flush pipe inside.
i only fit them not design them and never had any come backs after fitting.
so i'm shall yours will be fine after a new seal is fitted.

just be careful when removing the flush pipe as the seals on the pan end can be a bugger if thats old and starts leaking.

yu can always drain the cistern and lift the syphon to get the new seal on.
and fit it dry.

hi-spec plumbing & heating (essex), June 2010

Thanks hi-spec plumbing & heating (essex),

Yes the seal is tapered, but it doesn't seem thick enough to be effective. I guess i'll have a look around for a thicker one.

Surely there must be a better arrangement for this junction. This way round there will always be an amount of water sitting in the bottom of the syphon having not made it down the flush pipe, as the flush pipe sticks up into the syphon too far. I would have expected the flush pipe to be wider than the syphon exit, so all the water would go down the flush pipe every time.

Cheers, i'll get hold of a new seal and try it. Is any greese or anything required on the seal?

Mr D, June 2010

Thanks for the reply but this is not a close coupled system with the arrangement you mention. There is a separate flush pipe linking the hidden cistern to the bowl.

The leak occurs where the flush pipe enters the outlet in the base of the cistern.

Cheers

Mr D, June 2010

(I have a cheap plastic hiddern cistern. )

concealed cistern.

( This seems like a pretty poor arrangement to me, as anyone looking at this would expect it to leak at some point.)

concealed & high/low flush cisterns have been like it for yrs with no problems.

(Also the rubber seal doesn't seem thick enough to seal up the gap between the outside of the flush pipe and the wall of the cistern flush.)

the seal should be tapered. the taper sits in the bottom of the syphon.

(What i want to know is if this is a typical arrangement, or has this been botched at installation?)

only unless the wrong seal has been fitted.



( Also how can i fix this properly so there are no more leaks in the future?)

fit a new seal
check the bottom of the sysphon/nut is not split.
and that the flush pipe sits in fully and not been cut to short or sits at an angle.

hi-spec plumbing & heating (essex), June 2010

What you describe is probably a Donut or Doughnut Washer - a thick, soft, rubber washer compressed hard by a metal pressure plate with a wing nut and bolt each side at the back.

This is a normal arrangement on a close coupled cistern - leaks here can often be cured by just tightening the wing nuts.

You may wish to squint along the join line from the side - the thick rubber washer should be relatively thin and above all parallel - sometimes the down pipe from the cistern is too long - interferes with the material of the pan and tips the cistern slightly forward - in this case you will not get a satisfactory seal unless you saw an eigth of an inch or so from the end of the pipe.

If you need to change it a Dounut washer kit may bought quite cheaply from a DIY store...

http://www.toiletspares.co.uk/images/st/st_CC_kit_doughnut_washer_new.gif

To gain access turn off the water supply to the cistern and flush it. Undo the water supply union. Remove the wing nuts from the donut washer bolts. Remove two screws holding the cistern against the wall. Gently lift the cistern vertically and tip any excess water into the pan.

Some people suggest sealant around the washer - I don't agree - it's a low pressure seal and the pressure plate should be good enough to stop water coming out if it's properly squared up and tightly compressed.

On reassembly do not overtighten the screws into the back of the cistern else it may crack - snug is good enough.

First time you do it expect to take 30 mins or so.

Good luck...

Peccavi, June 2010