Soil pipe partial replacement

Not a lot of people as cutting in to an old soil pipe normally end up loosening the fixings and if the top is corroded it means the inside could be about to completely go I would recommend renew the whole soil pipe as you will just has someone back in a year or 2 to replace any way

Hi Nigel This sounds possible but you would need a lead to plastic connector. It might also be worth having a look at just painting the soil stack as a cheaper alternative as it sounds like there are no waste water connections from your description

a qualified plumber, but who ever does it he needs to be carefull these old pipe are held to the wall with spikes, these will be corroded as well.

Agree with blus plumbing solutions also, In my opinion it would be much safer and practical to replace the whole soil stack rather than part of it. removing part of it and replacing it with black PVC will cause more bad than good. like you said in the above you don't want to disturb the the rest of the soil stack but deciding to saw off the top part of the soil stack will do exactly that. In my opinion a new soil stack in black PVC will look a lot more neater than having a 50/50 use of material then in a few years down the line having the other half replaced.