Sweating Toilet - has anyone insulated theirs?

6 Sep 2016
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United Kingdom
I was aware of the problem with the old toilet that it would sweat a bit ( condensation) - it was dealt with by just wiping it up+ I thought It was leaking because of the amount of water everywhere , However now that I have re-done the whole bathroom ,including replacing some rotten floorboard underneath and installed a new Toilet I can only see how sewere the problem is and that it's actually just 100% condensation problem from the chilly water entering the toilet cistern.
Having done some research on this ( not that many resources...) seems like the only 2 solutions are: mixing in some hot water or insulating the cistern/toilet. I have tiled in all the pipes and it would be a total mess now to do it so that's kinda the last resort+ I don't think it would be wise to have warm water in toilet so the bacteria can thrive.

So that leaves me probably with just insulating the hell out of it, I'm fairly positive a lot of people have got problem with this in the winter ,was wondering if someone has tried to insulate theirs and how did you go about doing it and what were the results?
-Expanding foam would be really messy , I have seen some use some Yoga mats? I got some thick XPS floor underlay that could be a good waterproof insulator, but how would you go about glueing something like that to the inside of the cistern so it stays there? Silicone perhaps?

Thanks in Advance!
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The british bog industry has never confronted the issue of warm moist air condensing on the cold surface of a mains-fed w.c. cistern.

(I have seen cisterns in Germany that have with a thin layer of polystyrene inside.)

Yoga mat and Sticks Like Sh*t (really) is as good approach as any.

Go too thick with the insulation and you'll reduce the flush volume.

Alternatively heat and especially ventilate the room more.
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Any close-coupled insulated cisterns out there?

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