Cast Iron stack

[craig51]

Hello all.

I have a room at the top of the house.

On the roof there is a drain for the water to run into and then down the cast iron drain etc.

This cast iron drain runs through the room and I've noticed recently a wet damp patch on the plaster where there is a connection in the cast iron bend.

So I smashed the plaster away and it appears the water is coming from where the straight vertical meets the s-bend piece where the ridge is. You can make out on the picture where the cast iron is damp.

This seems odd as water should be flying down that pipe so not having the chance to leak out. Could I also maybe have a blockage too? What's best to seal that lip bit where it's leaking?

See picture for details.

 

[avonmouth]

The water might be from around the outside of the pipe and not inside ?
If so check the flashing around the pipe.

 

[ree]

As above.
But first: dry off the damp with tissue - dry off the lead joint (the ledge) and the pipe above it then wait for rain or go on the roof and water test around the gulley or grating, and then pour water down the pipe itself. Check for results each time.

Is the roof a flat roof? Or is the CI drain pipe coming from a gutter?

Pics of the inlet to the pipe would help, esp in terms of a possible blockage, and pics of the roof area.

 

[craig51]

It's a flat grp roof.

The vertical piece is dry, it's only wet from the ledge bit then down the bend which makes me think it's the ledge bit leaking.

But in my mind why? Even if it wasn't sealed water falls, so for it to go up I am assuming a blockage.

I have a cheap Endoscope so will go up, ensure there is no blockage and then a hose and test as you say.

Assuming no blockage , what's best to seal it, copious amounts of silicone?

Ps, by ridge I mean the top one. You can see the wetter part on the right hand side then working its way down to the lower ridge then down the underside of the bend .