What size CI is this (and which Fernco donut to buy)?

[EthylOH]

Hi all,

I'm trying to transition from CI to PVC on my main stack for a new drain line.

I need a Fernco donut, but there are two available (service weight and XH).

Looking at the markings on the 4" toilet elbow, I believe that it is the XH type CI.

However, the 2" hub looks much smaller than the XH donut fitting. Is it possible that it could be a combination of service weight and XH? Or are my eyes deceiving me?

I guess what I really want to know is which donut to order. (Home Depot has the service weight one, but the XH is much harder to find).

Thanks in advance!

 

[hj]

There is no such thing as a "combination size", but the hubs were never designed for use with a donut either, so you have to try to find one that fits YOUR hub.

 

[Sponsor]

 

[Jadnashua]

Fernco makes LOTS of different sizes because there is no such thing as a consistent sized hub from one manufacturer to another.

The only thing that is standard is the ID, not the actual size of the hub.

 

[hj]

In fact, some "mold cast" hubs will NOT work with a donut.

 

[Asktom]

I have had good luck packing in oakum tight to within an inch of the top of the hub and then using Black Swan "Soil-O" on top of it.

 

[EthylOH]

Well other than buying a dozen donuts in different flavors, how does one decide which is the correct size?

 

[Reach4]

https://www.fernco.com/plumbing/donuts-o-rings/donuts says

• Donuts can be ordered by giving the size, material and type of connection you want to make. Donuts require specific information on the manufacturer of pipe. Our sales coordinators are trained to assist you.
• Donuts can also be ordered by dimensions. Donuts seal by compression and have much less dimensional range than couplings. The bell, hub or socket dimensions must be given within 1/32" accuracy.

 

[Jadnashua]

IOW...MEASURE! If it's too loose, it will leak, if it's too tight, you may never get the pipe installed.