View Full Version : Tee PVC into Cast Iron Drain

12-01-2008, 11:03 AM
Putting in a new bathroom upstairs and are running a new 3" PVC stack down to meet with the main drain line in the basement. Rest of the house is hubbed cast iron. Have dug through the basement slab and am about to snap the 4" cast iron and T the PVC into the main waste line. My plan is to use a 4x4x3 PVC Wye and glue a few inches of 4" PVC into the 4" ends of the wye and use shielded hubless neoprene boots to connect the 4" PVC stubs to the cut ends of the 4" cast iron pipe. Is there a fitting designed for this or is this the best way to T a new PVC system into an old cast iron system? Seems like a kludge to me, there must be a better way.

Additionally, is it preferred to dig out an entire hubbed length of the cast iron or is it OK to just snap cut out a small (18") section and replace with a PVC T as described?

Thanks for your help!


12-01-2008, 12:06 PM
If you are cutting into the cast stack, use a cast tee.

Once the tee is in place, you can run off of it with PVC

12-01-2008, 01:16 PM
I am cutting into the horizontal run under the slab. Is a cast hubless Tee still preferred in this application?


12-01-2008, 01:41 PM
Horizontal? You could go either way,
I like using the no-hub cast wyes though.
It's closer to the pipe size and looks a bit cleaner.

12-01-2008, 07:25 PM
It also takes less pipe removal to get it in.

12-02-2008, 11:21 AM
Make sure you tee in in ten pipe diameters from any branch.

12-02-2008, 03:19 PM
Thanks for all the tips everyone. This site has been an important resource for my whole plumbing project.