40mm PVC pipe to 110mm cast waste pipe

[DIY Dad]

Hi folks, I'm new to the forums and looking for a wee bit of advice. Having recently bought a new home I've found a leak under the sink which needs repaired.

I have a 40mm PVC waste pipe going from the sink into a 110mm cast iron stack, which is packed with what I think is Plumbers Mate or something similar which is very soft and pliable (see photos):

Advice from the guy in a local plumbers merchant is to dig out the sealant and repack it with Plumbers Mate, Putty or even silicone 😱 ...is there any other simpler solution, like some kind of reducer to connect the cast to the PVC?

Any help is greatly appreciated 🙂

 

[ShaunCorbs]

What is the dia of the cast looks more like 2.5-3" ??

 

[DIY Dad]

What is the dia of the cast

It's definitely 110mm ...4 1/3"

 

[ShaunCorbs]

McAlpine DC2BL-OS Offset Drain Reducer Connector - Black: Amazon.co.uk: DIY & Tools

 

[DIY Dad]

McAlpine DC2BL-OS Offset Drain Reducer Connector - Black: Amazon.co.uk: DIY & Tools

Shaun, thanks a bunch 😀
Cheers

 

[snowhead]

There will be a piece of copper or lead into that cast iron with the plastic connector onto it. I bet the condensate from the boiler hasn't helped.
If that's 40mm plastic, then it's not 4" internal cast, it'll be 2.5 / 3 as Shaun said.
The collar on the cast is about 15mm thick.

You may end up using something like this, sizes would need confirming first over the outside of the cast;
Fernco Adaptor Coupling 112-102 / 45-38mm Grey | Priority Plumbing