Reducing 110 plastic to around <90mm Cast Iron Soil Pipe

[chossy]

Hi everyone, just joined. This is a great place with loads of amazing contributors, hopefully someone could help me out and maybe I could help someone else out in time .

I currently have a dormer build I am undertaking for a new bathroom and I have hit a snag with my soil pipe... I wish to attach to the existing cast iron pipe to 110mm plastic fittings but the adapter I got with the rubber fins doesn't slot into the cast iron pipe, I have taken rubber fins off still no dice. It looks about 85mm... I can't seem to find any 110mm to 85mm adapters that I think would work... every one I seem to find is an offset one which doesn't look like it would work for me?...

Thanks for any help you guys can give me.

 

[chossy]

Time saver coupler I think will sort me out.

 

[Ian H]

Are you doing this at ground level?

If you are have a look how far down the cast iron goes before it changes to clay. Your fins would fit in the clay.