New install -- copper closet bend

Hi All,

I will be installing a new toilet. I need to cross a 2x10 joist with the toilet drain. Max hole size, per code in a 2x10 would be 3-1/16 inches. I'm planning to double up the joist, but for PVC, hole size needs to be 3-1/2+ inches whereas copper can be 3-1/8+ inches. I'm leaning towards the copper as the hole size is smaller. As soon as I come down from the toilet, I'll elbow over and go through the joist, transition to PVC and then I will elbow again to follow parallel to the joist. Sound good?

As it happens, I have a good length of 3" copper with a 90 degree already elbow in it--I was planning on reusing this. It's dimensions appears to be a NIBCO 907-3 wrot elbow. This will essentially be my closet bend. Is this okay? As soon as I transition to PVC, I'll use a banded rubber coupling to transition to a long sweeping PVC elbow...

What type of flange would I use on this pipe and can I attach it after the flooring is in place?

(Editted: I've added a drawing showing this in section): View attachment Master Bath Toilet Drain Section.pdf

Thanks,
Jason

Jason, you will have to get a brass/copper toilet flange and you may need a short piece of pipe to go to the 90, then, you will have to solder it.