Compact toilet cistern leaks despite new rubber donut fitted.

[horseunderwater]

In 2006 we had a new Bathroom fitted top to bottom.
The chaps who did the job, guaranteed to stop any water leaking as we had previously had many a leak from the old fitments.
They put in one of those loos that has a small compact cistern with a push button flush and this sits against the wall. I had to replace the internal flushing fitting last year as it broke. Your help was great.
However, it still leaks from underneath where the 2 pieces join even though a new rubber donut ring has been replaced recently. It has been tightened as much as we can, but still it comes out. Not as bad as it was, but enough that there is a problem. Now call me daft, but the cistern looks like there is more rounded edges at the back and the front is flatter? Does that make sense? Is it possible to fit one the wrong way round? The inflow pipe is on left as you look at it straight on, but the inflow pipe comes up from the right and crosses over with a flexi pipe to this and an inline shut off valve. Could this be why it fails to seal correctly? Any advice appreciated.

 

[Best]

Guess it is possible to fit a cistern wrong way round! If it has no holes for screwing to wall like some & is glazed front & back, that is! 😀 Do make sure it is correct.Where water enters varies on toilets. Some cisterns need to tilt back to be seated correctly, ie touching wall at top only. My guess is it just isn't sealed right. A lot are not well made & often u have to improvise. Needs taken apart, check flush valve sealing ok. Then it's maybe worth renewing domed washer. Some guys seal this washer to pan ( only!) with a little silicone, on troublesome leaks but u risk permanately bonding cistern to pot!

 

[WaterTight]

Permanently? Most of those who use sealant use silicone and if it doesn't work you can just pull the cistern off and pull the silcone off. And it may make the difference. Healthy squirted circle between all surfaces involved (pan to doughnut - doughnut to cistern.) I've never found you need to tighten wingnuts as "tight as you can" and if it's the type whhere the bolts pass through a plate rather than a cistern overtightening will cause a leak by pull syphon's plastic nut away from cistern base.

Check cistern is right way round - curve at the back and flat at the front sound wee bit suspicious to me. While dismantling look at it both ways see which one sits right and looks right.

Silicone is considered a bodge in much of plumbng where it is visible and where the pressure of water acting upon it is likely to make it leak again before long. But on a toilet you can't see it and the toilet flush is usually quite low pressure (which is why toilet leaks are annoying and sometimes don't show up until three days after you've left) and so will hold for good. Yes it make the next time you need to take the cistern off involve a bit of tug and huff but nothing serious.

 

[Best]

By " permanately" I mean not to overdo amount of silicone as many tend to & completely unnecessary. If silicone is between the ceramic surfaces & gets fully cured, it could be a prob later. I use silicone washer to pot, on some problem ones & it stops leaks.

 

[horseunderwater]

So it might have been fitted wrong to start with and then re fitted wrong by us as we copied how it was.
Now that is interesting.
The cistern is glazed front and back and seems wider at what is currently the front and is more square, while the back is narrower and has more rounded corners?
I reckon we need to totally take it all apart and start over. As it is an upstairs one, I need this sorting as I do not want more water pouring down into dining room as that is always where it goes.
As to silicone - pipe it round hole of base and round the bit abover the rubber ring? Is that right?

 

[Plumbstar Tom]

sounds to me like it might very will be back to front

is it a branded cistern that you can check pictures on manufacturers website?

 

[royston]

There are a few different types of close coupled washers. I find the large foam ones are good as they seem to compress more as the rubber ones dont Bit of silicon between donought and pan wont hurt.

 

[johnnyplumb]

dont use silicone- makes it difficult to remove & you have to wait for it to cure. use plumbers mait or putty all around the doughnut washer and bolts. if doughnut looks worn replace it as well.

 

[WaterTight]

I genuinely find silicone less annoying to remove than plumber's mait.

 

[royston]

I genuinely find silicone less annoying to remove than plumber's mait.

Yeah i agree.

 

[horseunderwater]

So we need to get a foam donut, some silicone and see if cistern sits better the other way round. I think we would then have to change inlet pipe to a straight up connection as it would directly above the water pipe. Should be an easier enough job to do.
Thank you chaps/lasses for help.

 

[Best]

I genuinely find silicone less annoying to remove than plumber's mait.

Yes, i hate plumbers mait also. If you put some below washer u risk some falling into inlet of pot & blocking it. Saw exactly this when a plumber had caused a loo to have water spinning in bowl in one direction when flushed. Wouldn't even flush a tiny bit loo paper away. :grin: