bathroom stuff i want to sort out......

got a patch of wall in our bathroom that [when painted] bubbles and flakes off.
i've been troubled by this for a while now, putting it down to the fact that the wall is an outside wall on the back of the property, which i dont think is insulated (cavity wall). its an old georgian building(?) like most terraced houses on our road. but i had a good look outside - i can only hang out of the window,(we're on the first floor, but the back part of the land slopes down, so we are actually on the second floor if you know what i mean) but what i can see is an old waste pipe sticking out from where this patch accumulates.
i think there must have been a sink there which has been moved and sealed off before we acquired the flat.
anyways, i thought 'how could this affect the wall in a way that would make the paint flake off?' i'll
take some images tonight, but what i really want to know is there anything i can paint/apply to the wall that will stop the ingress of any water - if thats the problem? the interior wall is covered in a porous grey plaster material.
i've tried waterproof PVA, but this bubbled and flaked off!
i've painted over the area again on the off chance that the PVA has done something. i should imagine it'd only take a week or so to show any signs of damage.......

next thing is our toilet. occasionally i find a small pool of water directly below the corners of the cistern. could this be down to condensation building up on the outside of it? or would it be wise to take it apart and replace the large o-ring seal that connects the cistern to the toilet basin..?? there is also a collection of blue/green residue that seems to come from inbetween the cistern and top of the toilet basin like copper oxide...

Try an oil based "stain block" paint.

Toilet probably condensation on the outside if its a direct fill from the mains water. You should be able to see it!

Re' the wall....

It sounds like there is damp being absorbed either from the outside by the pipe itself (the pipe will be creating a "Cold Bridge" and allowing condensation to be absorbed into the bricks, or the pipe itslef still has a water feed to it behind the brickwork, which is leaking....

PVA will do nowt, as the damp is originating behind or underneath it, and will still bubble up.


Toilet....

Is the loo on the outside wall too?
This will 99% be condensation, and should be visible on the verticle bits of the cistern.
Is the bathroom/privvy heated sufficiently? If its chilly, then the condensation will be encouraged

Maybe look into getting the property surveyed for free by a local Green Deal Assessor.
They will make objective and impartial recommendations on "whole house" home energy efficiency, not just the particular issue you are asking about (be it insulation, a boiler, solar etc) and will provide you with a free report detailing energy savings, cost savings, and other things you havent already thought about


G

is there a gutter or downpipe close to that wall? you'll be suprised how many people think they have rising damp when sometimes it's nothing more than a gutter that needs cleaning/sealing or both