Advice on fitting a Close Coupled Cistern to a Toilet Pan

My advice to anyone fitting a new or replacement Close Coupled Toilet are as follows:-
Firstly check Cistern is glazed underneath where it sits on the back of Pan as a lot of them are not these days if it is not I would suggest that you may wish to return it or possibly use a proprietary water proofing sealant before assembly as otherwise the unit may have the same properties as a terracotta flower pot completely porous which will seep water (This is due to modern cheapened production methods being used). Problem is you don't know until you unbox it if it is glazed on the bottom or not!

The bigger problem however is this :- All the fittings that go through the base of the cistern require more adequate sealing than what is suggested in the assembly instructions.
This is due to poorly finished holes with small lumps and bumps which prevent a nice flat surface to mount fittings on.
I would suggest as a matter of course that the rubber cone washers & the rubber flat washers which are sandwiched between the 2 penny washers that go on the bolts through the cistern and then subsequently through the pan have a small amount of silicone sealant applied to them, I would also suggest that a smear of silicone sealant is put on the threads as well as I have known water to spiral down the threads !
The large plastic thread which the flush unit has requires a rubber or polythene washer externally with some silicone before tightening the nut as does the fill unit fittings. Having done this and allowed to dry sufficiently I would suggest you fill the cistern and check for leaks before bolting to the Pan.
Many people think the leak is coming from the large foam rubber donut which is sandwiched between the Cistern & Pan but in my experience this is not the case but the above are what usually cause the problems.
Although all this may seem a lot of messing about,I think its worth it as if you do this hopefully you will have a leak free Toilet first time and won't be required to remove again once or maybe twice to resolve problems which can be annoying & sometimes costly.

 

Dave ,Thanks for your quick response Although Normally I would agree with you regarding the use of silicone as in this instance it is only being used externally I have not had issues with removing problems in this application and the main issue I have is the quality of the toilets that are being supplied these days the imperfections in the porcelain . you will see loads of threads of peoples problems with a whole range of toilets leaking on installation or shortly after not just cheap price ones. So what would your suggestion be to overcome this ?

 

I know what you are saying regarding the wall leaning or not square to the floor.
Re plumbers mate is that really used that much anymore ? Loctite do a good range of modern sealants for different applications which are better however a lot of people wouldn't always have these to hand. I Have read my original post again & realise I may have not explained what I do that clearly. Regarding the bolts that secure the cistern to the pan I stand by what I said as the likelihood of those to require replacing in the life of the toilet is unlikely.
However if you use a polythene or thin rubber washer ( I prefer polythene due to the thickness) on the outside of the cistern and then a ring of silicone sandwiched between another washer before fitting the securing nut on the flush unit thread this takes out the unevenness of the porcelain but doesn't slare up the threads which you rightly said can be difficult to remove. You may not agree with me that you have found this is required thats fair enough but I just wanted to help out all those people who have to keep taking their new loos apart to try and resolve their leaks, sometimes messing up their new decor in the process.