Replacing 3" Copper with 3" PVC

[itsr-ent]

I need to replace a small section (about 3 feet) of horizontal 3" Copper waste line. This is part of a longer run (about 10 feet), but only a small section has been damaged. I was planning to use Fernco Proflex transition couplings (#3001-33) to replace it with PVC. These are specifically designed for the 3" copper vs 3" PVC size difference.

My concern is that with the PVC being larger than the copper, this will create a 3 foot section of "lower" area within the piece of PVC for waste to collect. Is this an issue or is the size difference not enough to cause a concern? I found online that 3" copper (L) ID is 2.945" and 3" SCH 40 ID is 3.042". However the copper wall thickness is .090 and PVC is .216...maybe the wall thickness difference will make them align pretty well?

Thanks!

 

[Reach4]

See https://www.fernco.com/plumbing/shielded-couplings/proflex-couplings.
Fernco Proflex transition couplings (#3001-33)
3001-33 3" CI to 3" Copper
That means it connects cast iron to copper, so you don't want that.

I think you want
3007-33 3" PL, St. or XH CI to 3" Copper,
which connects 3 inch plastic to 3 inch copper.
Clicking that number below gives https://www.fernco.com/dimensional-drawings/3007-33
Note the A and B dimensions are different. Check the numbers, and don't rely on what I wrote.

I am only going by the web page and not experience.

 

[Sponsor]

 

[itsr-ent]

Oh, thanks, I didn't see that one. I was just going by that all the smaller sizes (like 2") seem to be for both CI and PL so I figured maybe 3" was too. So I will definitely use #3007-33 instead.

Still curious if the alignment of the pipes will cause waste to collect in the PVC.

 

[hj]

The I.D. of the pipes is the same so if you line them up properly, there will NOT be a "dip".