Drilling a cast iron soil pipe

[endecotp]

Dear Experts,

How hard is it to drill a cast iron soil pipe? This is to connect a condensate drain from a new boiler. The options are:

(1) Outside to a cast iron rainwater pipe.
(2) Inside to a cast iron soil pipe (which involves opening up some studwork). (I'm in a ground floor flat, it serves 3 flats above me.)
(3) Pump, running to a kitchen sink drain - which would involve poking pipes under floorboards and behind kitchen units.

The aspect that is totally unknown to me is drilling into a cast iron pipe, in order to fit a boss for the new 22mm pipe, for (1) or (2). I've had a heating engineer visit to look at the boiler installation generally and he seemed unenthusiastic about it. Is there a danger of breaking the pipe, for example?

Please share your thoughts.

 

[Mottie]

What does the heating engineer recommend?

 

[endecotp]

What does the heating engineer recommend?

He seems to like the idea of the pump, but he’s never tried to feed pipes under my kitchen floor, nor deal with the sink drain when it gets blocked and needs to be vacuumed. I think I’m going to ask him to route it to the soil stack. We only spoke about it briefly. I’m just looking for any experiences you can share about drilling cast iron.

 

[Mottie]

The lower part of my soil stack is cast, the upper half is some sort of cement/asbestos material. I drilled into my upper half where it went through the roof to fit a boss as my boiler was in the loft. It was a job and a half!