What's causing this water line on my hallway wall??

The_Walker

I'm looking for some advice here. I'm having a battle to prevent a line of "condensation" appearing on a wall and running down it ruining the paint. I have since painted the wall with damp resistant paint (the white area), and while it works on other areas of the flat, this wall is still a problem. The line is directly where our 1st floor flat divides from the ground floor flat. I suspect a hot water pipe runs in the wall from the kitchen boiler to the bathroom, but I'm not sure. The pipe may actually run in the floor instead. The hall is very cold compared to the flat.

I can only think of 2 causes:

1. A hot water pipe is leaking or causing a temperature difference

2. The difference in temperature between top and lower floors is the cause

Any ideas? How can I stop this?

Thanks

Emmia

What is on the other side of that wall - I can see a windowsill above the line - is there a flat roof or something that is at that is at that level?

The_Walker

No there's nothing outside the wall. It's just flat and with no marks on it.

gerdo

You can get cheap devices that detect pipes in walls, might be worth buying / borrowing one to see if there is a pipe in that wall.

stuart45

I've got a similar problem in the kitchen with a cold water pipe.

DorsetLad

I was also thinking it could be a cold water pipe, which is making that part of the wall colder than the rest, so making it the first place for condensation to form if there is humidity in the air. This would explain why the dampness is a line, rather than the more rounded patch you might expect from a leak. As suggested above, try to get hold of a pipe detector to verify. Solution (if a cold pipe is the cause): can you ventilate that part of the flat better? Can that window be opened a little for ventilation?

Homer_home

That would be a totally random place to run a water pipe , as that is clearly an outside wall I would be looking at your pointing

Any chance of some pics of the outside wall from the outside?

frayedknot

Homer_home said:

That would be a totally random place to run a water pipe , as that is clearly an outside wall I would be looking at your pointing

Any chance of some pics of the outside wall from the outside?

Not really random , the pipes have to run somewhere and it's flats so anything usually goes.  What are you hoping to see outside? The pipe runs along the inside of the wall, it will be a cold rising main so quite cold particularly in winter and may cause condensation. With it being flats i.e bodge central , i bet the pipe is about 2mm under the plaster.

The_Walker

There's not much going on outside. A drainage pipe outside does run pretty much parallel with the mark though.

welshmoneylover

Where’s the roof?

The_Walker

welshmoneylover said:

Where’s the roof?

It fell off.

No actually it's one of those wonderful flat roof properties that requires endless maintenance and then still leaks! And the council refuse to let owners put on a decent roof.