Difficult leak on waste stack in block of flats

[tbokris]

Hi all,

Excuse the length but this seems like a complicated fix.

I lived in a 1930s block of flats. Brick building with concrete slab floors.

The waste stack is internal and bricked into corner of the bathroom. I noticed paint peeling and brown staining recently at the bottom near the floor, and I opened up the riser and see whats going on.

Turns out there's two leaks - a big ish one on the bath waste water pipe coming down form the upstairs flat, that leads into the cast iron stack. This one has been fixed with fernco and a new small section.

There also is a leak on the length of lead piping that goes into the stack itself. The leak isn't visible, but it seems to be on or around the wiped joint where a lead waste pipe couples straight into the cast iron.

The cast iron runs the up and down the whole building, with all flats being the same layout, however because the flat above me is in the mansard roof and is inset, it looks like the waste pipe converts to lead in my flat before going up into the concrete slab floors as a lead soil pipe. see diagram.

It seems the obvious thing would be to get rid of a lead section entirely. The only problem is the lead goes up into the poured slab above and then serves that flat before appearing again as a vent sticking out of the roof. Renewing all of the lead section would involve massively taking apart the flat above's bathroom and the roof to the block of flats.

The waste pipe is the responsibility of the council, and their plumber from Mears came round and doesn't know how to fix it. He seems to say that you can't chop out the cracked section of lead and renew just that section, because of problems attaching the new section to the good section of lead. Fernco apparently might not make a good seal because the lead might not be perfectly round. Going into the cast iron end is fine, but connecting to the lead before it dissappears into the ceiling is the issue.

The plumber caked the problem area in CT1 and Denso tape and says that's all he can personally do, without referring it back to the council. The leak is about 50% better.

(For ease, in the diagram I have not drawn the smaller fernco-solved bath waste pipe which was copper into the iron)

Perhaps it's wishful thinking, but the larger leak lead me to find this smaller leak, which I don't think I would have even known about. It's a soil stack leak and so is gross, but it is not leaking that much. Part of me wants to just box it back in. It dribbles down the cats iron, but not so much that it reaches the floor, so the floor will no longer be getting damp. Provided this lead leak doesn't get worse.

Does anyone have any ideas?

 

[ShaunCorbs]

Need to replace the stack as it’s getting old and starting to cause problems

 

[Ric2013]

Realistically, the pipe isn't under pressure. While I see the point about the lead may not be perfectly round, I think that if the lead, or a new continuation from the lead were to go INTO the cast socket rather than rely on sealing to the outside of the socket, water would stay inside. Which may leave the possibility of sewer gasses escaping but any leak of foul air could then be sealed externally with LSX.

It's not do-able to make the joint in your flat as you are so close to the ceiling. The plumber could potentially cut the cast iron lower down, or, alternatively, replace a section of pipe from upstairs down to your socket and joint to the lead on the floor above.

You could get a skilled worker who could weld up lead? Us youngsters, sadly...

Or, realistically, it may be cheaper to look at a new stack, as Shaun has suggested. Goodness knows why people think hiding things inside walls is a good idea. Makes maintenance very hard.

 

[tbokris]

Realistically, the pipe isn't under pressure. While I see the point about the lead may not be perfectly round, I think that if the lead, or a new continuation from the lead were to go INTO the cast socket rather than rely on sealing to the outside of the socket, water would stay inside. Which may leave the possibility of sewer gasses escaping but any leak of foul air could then be sealed externally with LSX.

It's not do-able to make the joint in your flat as you are so close to the ceiling. The plumber could potentially cut the cast iron lower down, or, alternatively, replace a section of pipe from upstairs down to your socket and joint to the lead on the floor above.

You could get a skilled worker who could weld up lead? Us youngsters, sadly...

Or, realistically, it may be cheaper to look at a new stack, as Shaun has suggested. Goodness knows why people think hiding things inside walls is a good idea. Makes maintenance very hard.

Thanks for your input. I think there’s enough by the ceiling to couple to the lead although the image doesn’t show it. I see that if the new pipe could go INTO the cast iron then that would work on that end.

The question is what would you use to couple to the lead?

I think if we replace the lead on the floor above we would have the same situation of how to couple to lead pipe this large.

 

[Ric2013]

Is the lead pipe small enough to fit INTO a solvent socket?

 

[tbokris]

Is the lead pipe small enough to fit INTO a solvent socket?

The lead pipe looks to be about 5" diameter, so not sure if solvent sockets go up that big in size?

 

[Ric2013]

Should be possible to get a PVC soil that is larger than 5" internal diameter.

 

[Timmy D]

First, ensure the exact position of the leak on the lead is found.

If in a workable area, cut lead just above/through leak.

Remove lead from cast socket.

Cement a section of plastic soil into cast socket.

Join lead and plastic with a Fernco or time saver coupling.