Cistern leaking?

[Martin Brown]

I have fixed the main original fault which was that the cistern valve was not cutting off and overnight the level would rise until it hit the overflow. The overflow avoided inconveniencing any spiders in the exterior pipe by dumping this water on the floor drip by drip. Resealing the loose joint properly has fixed this big leak - but...

The toilet cistern still appears to have another strange fault where the base is slightly porous and unglazed leading to a slow drip. The glaze does not extend to the underside of the thing. I cannot see any hairline cracks or obvious defects.

My next step will be to put newspaper underneath overnight and watch to see where the latest slow drips are now coming from.

It is also possible that condensation from the steamy bathroom onto the cold cistern surface and then dripping down. If it is a glaze defect any suggestions what to add to the tank prevent it leaking?

I have in mind something like sodium silicate, Fernox or PVA. My dad has clearly painted the (leaking?) underside with ahem something. It doesn't appear to have made any difference though.

I am pretty sure that something else is still wrong with a very slow continuous leak still present but as yet cannot figure out what it is...

Any thoughs for a better way to diagnose or how to proceed?

Thanks, Martin Brown

[Dave Liquorice]

The outside underside of most cisterns isn't glazed. The inside will be fully glazed to keep the water in...

My bet would be condensation drips.

[Hugh - in either England or Sp]

I have had 2 dripping cisterns in the past. Both cloakrooms where mains water came straight into the cistern at a cold temperature resulting in condensation. Placing newspaper under the cistern will only show where the drips drop from. Fastening something absorbent to the cistern will give a better idea where the water originates

[F Murtz]

I had a problem once like that,the float valve was spraying a fine jet of water upwards on to the lid and was then dribbling slowly down the outside of the cistern. another problem I have seen is water collecting on the floor round the bowl, the cause was that the householder hung those coloured antiseptic doovers in the bowl which was causing turbulence which caused an amount of water to splash over the side and dribble down outside.

[Muddymike]

+1.

Mike

[The Natural Philosopher]

+1

fit extractor fan to bog..

When I was slating my new kitchen one very hot summer I was disturbed to see drips forming on the base of the newly installed incoming cold water pipe. I feared a leak. Until I realised that I was dumping gallons of water onto the screed in terms of tile cement, and that the cold water pipe was about 15 degrees below ambient temperature.

[Brian Gaff]

I've never heard of that sort of leak that was not visible. Its usually condensation that does this kind of thing. It seems to be worse on systems which use mains water directly, and not so bad on those fed from loft tanks, presumably due to the temperature of the water being different.

Brian

[Brian Gaff]

Obviously what he needs is a double glazed cistern, or a patent incoming water warmer, but as has been suggested, its the humidity and the temp difference that generally causes this, so a fan or a dehumidifier might be more easy to come by. Brian

[Chris Hogg]

As several others have said, condensation due to the low temperature of the incoming water and high humidity in the bathroom/toilet.

Assuming the cistern was made in the last 25 years, perhaps a bit more, it won't be porous. These days they are a form of porcelain and fired to a sufficiently high temperature that they become fully vitrified and non-porous. There is a British Standard that they have to comply with (used to be BS3402: 1969, but probably superceded by now). Being glazed or not being glazed, whether inside or out, top or bottom, won't make any difference to whether water can soak through: it won't in any circumstance. OTOH if it's some ancient Victorian cistern, then it may well be porous and could possibly leak if the glaze doesn't cover the entire surface.

But my money's on condensation. We get it on ours in the winter.

[<me9]

I've never seen an internally glazed one. Even if the ouside isn't glazed it won't be particularly porous.

Either that or a leak from a fitting (unless obviously cracked), I'd put my money on condensation too.