Small leak in Twyford Syphonic loo cistern

[nmw01223]

In our cistern, there is a very small leak, maybe 2 to 3cc overnight. Seems to be coming from where the overflow pipe exits the bottom of the cistern (it's a vertical copper pipe that rises from the bottom to just above the filled water level, below, it turns horizontally and goes through the outside wall).

There appears to be some blueish sealant round the bottom where it comes up through the base of the cistern, though it's very old.

Wanting to find some sealant I can put round that to see if that solves it before considering anything more drastic. Found some waterproof sealant called Adiseal - can even be applied wet, it says - but on tslkinggto Adiseal they say this is waterproof, but not recommended for permanent immersion, and this will be at the bottom, under about 12" of water in the cistern.

Can anyone recommend the best sealant for me to use?

 

[breplum]

here in the USA we don't have anything like what you show, so can't offer a lot of advice. We don't call any plumbing parts 'cistern'.

 

[RS]

My son that lives in New Jersey says toilet tanks are commonly called cisterns in his area, so I know what your talking about. I think I remember a rubber gasket between those 2 parts, but it's been a long time since I worked on a toilet. I would thin you need to remove the cistern from the loo and clean the surfaces very well, and if there was a gasket there get or make a new one. And you should find some sealant for continuous immersion.