View Full Version : Cast Iron Shower Drain Replacement (Slab)

07-15-2008, 08:55 AM
Hello - I am currently remodeling a bathroom with the intent to use a Kerdi drain. I have finished demo and have started on the drain. The house is ~47 years old and the drain is all cast iron. I am looking for some recommendations on how to proceed forward. The picture below shows the current state of the drain. I would like to cut the drain behind the p-trap and use a Fernco no-hub coupling to attach a new PVC p-trap and riser. Is this the correct solution for replacing the cast iron p-trap and riser?



07-15-2008, 09:43 AM
You're on the right track!

07-20-2008, 05:32 PM
Redwood - Thanks for the advice, I went out and purchased my pipe and fittings and started excavating some more to cut the cast iron. I uncovered a cast iron hub and I'm not sure how to proceed. It seems I have three options here....

1) Cut off the cast iron p-trap leaving enough material coming out of the hub so I can attach the no-hub fitting.

2) Excavate more of the slab so I can cut off the hub, then use a no-hub fitting to transition to pvc.

3) Remove the pipe out of the CI hub and use a donut fittings in the hub to transition over to pvc.

What is the best way to proceed forward here?


07-21-2008, 11:40 AM
I'd really appreciate some advice here, anyone???

07-21-2008, 11:53 AM
Hi Justin,
As always in plumbing there are several ways you could do the job and in this case 3 that I can think of and all would be correct.

1 You could cut the old trap off just before the hub and use a no-hub or other banded coupling to join on the new trap. You may have space constraints that you need to check. See if you do this that the trap will line up where you want.

2 You could remove the old trap from the hub, clean it all up and use a donut to install the new one. Again make sure of space constraints.

3 You could cut the line after the hub and use a no-hub or, other banded coupling to install the new trap.

Option 1 is the least amount of work. The other two would be more work.

03-24-2009, 01:28 PM
Update: I know it has been a while but I am getting ready to finish this project up this summer. Here is where I'm at, I have the drain fully removed and capped off with a fernco blind cap right now. I am getting ready to bust into the adjacent closet to make a walk in shower, to get the new drain location I will have to make a 135 degree turn out of the existing cast iron drain stub (see sketch).

Can anyone tell me if my proposed plumbing layout in the picture below looks OK? Are there any issues making this kind of turn in my drain line?


03-26-2009, 03:14 PM
I'd bust cement and make it a straight run.