Advice for transitioning PVC to non-standard cast iron

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seanp

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I'm in the process of remodeling a small bathroom and am moving/upgrading the toilet and waste line. The plan is to use 3" PVC for the new waste line and tie it into the existing cast iron -- the transition will be under the floor. However, I have a dilemma in that the cast iron appears to be a bit non-standard -- using one of my clamps as a set of crude calipers, the OD of the cast iron is right around 4-1/8". So, I'm effectively trying to transition from the 3-1/2" OD of the PVC to the 4-1/8" OD of the cast iron.

I have a Fernco 1059-33 that I was planning to use -- it specs out at 3.49" on one end to 3.90" on the other. Recently, though, I read that even under a floor it was advisable (and maybe even code?) to use a shielded no hub transition for this application due to shear resistance. I also saw another post of Terry's indicating that 4-1/8" is really a copper pipe OD (for 4" copper), so using no hub fittings for copper would work best. I've looked at Mission's stuff, but they don't appear to make a shielded fitting for 3" plastic to 4" copper. The best I can come up with is to add a 3" coupling to end of the PVC which would bring the OD out to about 4", then use the Mission 4" copper to 4" copper fitting (K 400) for the transition, however this seems like a bit of a hack.

Just wondering if anyone has encountered this situation before and has a better solution?
 

Terry

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A 4x3 flush bush into a 4" plastic to 4" copper Mission coupling.
Now you can glue the 3" to the flush bush fitting.

And yes, 4-1/8" is a copper size.
 

seanp

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That's a better solution -- thanks, Terry. I wasn't aware of the flush bushing fittings, but it looks like that will do the trick. Thanks too for the forum -- it's been really valuable and I've learned a lot from reading through old posts.
 
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