Service Cast Iron Adapter Confusion

[delaware]

I'm adding a drain connection to a 110 year old stack which I've determined is a 4 inch "service" cast iron pipe (outer diameter 4.3"). I need to couple a 4" Schedule 40 PVC pipe to it, but that has a 4.5" outer diameter.

Obviously the standard 4 x 4 Fernco flex couple won't do the job, and I've been scratching my head on how to do this. I came across this other Fernco product for service weight C.I. pipes (Multi-Tite):

https://www.fernco.com/plumbing/donuts-o-rings/multi-tite-pipe-gaskets

I'm confused about how this works. I would assume I need the 4 x 4 variant (SVG-4) and I'm guessing I need to shove the donut into the cast iron. But on inspection of a unit at Home Depot, I found that a 4" PVC pipe fit inside the top opening, but the other end looked like it would be way too big to fit into the cast iron. If I use brute force, won't that distort the ring and lead to blockages?

And assuming I figure out how to use this thing, do I then need a standard 4x4 Fernco on top of everything?

Thanks in advance for any guidance on this

 

[frodo]

the OD of the pvc pipe and the OD of cast pipe

2'' cast od ........... 2'' pvc od
2.30 .............2.375
3'' cast od...........3'' pvc od
3.30...................3.50
4'' cast od...........4'' pvc od
4.30.....................4.50

it will fit, but I am WARNING YOU..IT IS TO BIG and has to be BEAT IN

using a block of wood over the pvc and a sledge hammer.

the gasket, fits inside a HUB not inside a pipe
it replaces the old oakum and lead joint

 

[Mr_David]

Be also warned,
Old cast iron can become soft and brittle.
Might not take a beat down needed to get it together.
use a mission coupling. they have different ones for transition between
extra heavy cast, standard cast, plastic and copper

 

[delaware]

the gasket, fits inside a HUB not inside a pipe
it replaces the old oakum and lead joint

That makes more sense, it's for the hub. That won't work for this job

Be also warned,
Old cast iron can become soft and brittle.
Might not take a beat down needed to get it together.
use a mission coupling. they have different ones for transition between
extra heavy cast, standard cast, plastic and copper

Interesting, I will definitely check out mission couplings. Will they provide a tight enough seal with the .2" smaller diameter going from PVC to cast?

Thanks buddy

 

[frodo]

if you use a proflex 3000-22 or mission cp-200

you can go from cast to plastic

 

[delaware]

you can go from cast to plastic

even with the smaller cast diameter?

 

[frodo]

https://www.fernco.com/plumbing/shielded-couplings/proflex-couplings