Simple wc toilet leak question

[mjbarnard]

New modern wc just installed. Close coupled pan and cistern. Pan is "back to wall" and cistern rests directly on top it. All connections satisfactory except those joining the pan to the cistern.

These are not the standard connecting bolts and plate.

Two bolts go through the bottom of the cistern and screw into fixings within holes in the back of the pan. They are designed to do this without anything between the pan and cistern.

Supplied are conical black rubber washers (and metal washers on top) to seal the holes in the bottom of the cistern. These leaked massively. So I added thin plastic washers between the pan and cistern.

I have undertightened, appropriately tightened and overtightened the bolts. One is fine but the other still leaks whatever I do.

What is the best way of sealing this connection? Fibre washers, sealant, different conical washers (I have tried white stiffer ones already) or what?

TIA

[Chris Bacon]

So you've got:

###### bolt head --##-- washer \\##// rubber cone =====##====== cistern floor ~~##~~ plastic washer @@@@@##@@@@@ W.C. bowl #### Nut

Something like that?

[Roger]

The message from "mjbarnard" contains these words:

What about the rubber doughnut? That goes between the cistern and the pan to seal the flush.

Can't see that those plastic washers would help. The conical washers seal by being forced into the holes in the base of the cistern.

It could be the hole is so misshapen that the conical washer just won't deform enough to seal in which case your supplier should replace the cistern with one that does work.

Sealant might work but if the cistern is defective it would be best to exchange that and get an easy seal.

Several years ago I bought a new bathroom suite from Focus with such a toilet but neglected to install it. I actually got round to fitting the pan to the stack this very week but I have yet to plumb in the water supply so I don't know if mine is going to leak. I have another toilet so there is no pressure to complete.

[Set Square]

Are you sure? I have a similar one, but mine has nuts under the cistern to compress the sealing washers. Then the threaded ends of the bolts pass down through holes in the pan, with further nuts underneath. Are yours not like this?

[mjbarnard]

Thanks to everyone so far.

Chris - the connection is exactly as you describe, except the bottom nut is actually built into the hole in the pan.

Roger - the doughnut works fine. It is actually a special very soft one supplied with the wc. Somewhat thinner and softer than the usual ones. However I can verify that the leak is from the connecting bolts - not the doughnut.

I agree the plastic washers shouldn't be necessary.

The hole in the pan doesn't appear misshapen. I suspect the fault lies in the shape or quality of the conical rubber washer.

Set Square - I am sure. The nuts under the cistern do exist - but they are incorporated into the holes in the pan. It is a modern designer type of wc - there is a flat bottom to the cistern which sits exactly on an exactly equivalent flat ledge on the pan. The pan extends right back to the wall. There is no room for anything in between. Originally I tried larger plastic washers between pan and cistern - but the cistern became unstable - all of it's bottom sits level on the pan.

[Chris Bacon]

###### bolt head --##-- washer \\##// rubber cone =====##====== cistern floor ~~##~~ plastic washer @@@@@##@@@@@ W.C. bowl #### Nut

So the cone has to compress onto the bolt (hope it's not a set bolt - does the thread go all the way up to the head?) as well as the cistern, else it won't be watertight. Not a lovely design IMO. The plastic washer won't help a lot, as of course water may pass it (between the bolt and washer) and seep through the threads of the captive nut. Does the cone fit tightly onto the bolt shank? If not, can you use a larger bolt (if you can replace the captive nut)? Could you use silicone to stick the cone onto the bolt, let it go off, and then do up the bolt with more silicone to seal it? 1/8" PTFE gland packing?

[mjbarnard]

Yes the cone has to compress as you say. The thread does go all the way up.

Agree not a great design. You wouldn't believe what it cost! I think the design is attributable to the 'back to wall' nature of the pan. The back of the wc is not accessible once installed, so the design allows removal/connection of the cistern to pan from the front/top without pulling the wc away from the wall.

Not quite sure what 'tightly' means. It appears a close fit - but the cone definitely feeds very easily over the bolt.

I could use a larger bolt - but am a bit wary of removing the captive nut. It is actually not a nut but a piece of metal with appropriately sized screw hole for bolt with metal wings underneath which stabilise it within its hole. If I remove it and fail - I might be worse off.

I could use silicon exactly as you describe. I might try this next.

Not sure what gland packing means?

[Chris Bacon]

Sounds like time to change the bolts - difficult, sealing to the thread...

A close fit should be OK, bearing in mind that the shank of the bolt needs the cone to compress onto it.

I should try to get another bolt (not a set bolt) - what's it made of, BTW?

Stuff that's used to pack glands, where a shaft goes through. Like a piece of cord, but made of PTFE, about 1/8" in diameter (these yanks!). Wind it around the shank of your new bolt to replace the cone. Just a possibility.

[Roger]

The message from "mjbarnard" contains these words:

FWIW the cones on mine are quite a tight fit on the thread. If the leak is down the thread rather than round the outside of the cones then silicone sealant on the thread should give an effective seal.

[The Natural Philosopher]

doesn' th erubber washer go bteween the cistern and the pan with the plastic washers inside the cistern?

Anyway, the answer is a shitload of silicone sealant - between pan and cistern and between washer and cistern base. finger tight, leave 24 hours, then tighten fully on custom made silicone rubber gasket...