3-1/2" Cast Iron pipe connection to PVC

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Old 06-03-12, 03:15 PM
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3-1/2" Cast Iron pipe connection to PVC

I am doing a bath remodel on a 1960s era home and an looking to connect my new PVC waste pipes into the existing cast iron pipes. I initially thought the cast iron was a 4" diameter pipe, and thus attempted to connect 4" PVC with a 4" to 4" shielded coupling and then a 4" to 4" inch fernco coupling. The connection with the first shielded coupling felt forced, and the connection with the Fernco coupling felt loose. I then realized that the cast iron pipe is actually 3-1/2 inches (listed on the outside of the pipe), with a 4-1/4" outside diameter. Apparently this pipe size is rare . . . I haven't been able to find much information on what type of connection I should use. I've read on a few blogs that that some have recommended a Mission C-44 connection. Is anyone aware if this is an acceptable product, or are there any suggestions for a way
to get a more secure transition. Thanks
 
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Old 06-04-12, 06:05 AM
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Have you been to a plumbing supply? They offer more than Home Depot. They should have a rubber coupling that works. A bushing that mounts inside the cast iron pipe sometimes works also.
 
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Old 06-04-12, 10:57 AM
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I then realized that the cast iron pipe is actually 3-1/2 inches (listed on the outside of the pipe), with a 4-1/4" outside diameter.
You may need to add a no-hub transition adapter on the PVC, then use a coupling made for the cast iron.
 
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Old 06-05-12, 05:27 AM
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are you sure on this. I did plumbing and heating for quite some time.....

Ive never heard of 3 1/2" pipe.

I cant remember but I believe for drainage you want interior diameter anyway not outside so it should be 3" pipe. Have you just tried measuring the inside of the rubber furncos in the store to see if they match or can stretch over? My guess is its 3" and you will just need a 3" cast to pvp furnco to join the 2 hubless ends.
 
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Old 09-15-14, 12:55 PM
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Just to add, I know this thread is old.

There are connections for this. Just bought one from Murray Supply in Medford, MA:

Cast iron threaded 3.5 inch male has 3 inch pvc female.

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