Reduced Waste Line?

Does this line reduce in size or is it just the difference in size from cast iron to PVC?


There is a reduction, but it is very slight. I wouldn’t be concerned with it. Mostly pipe thickness difference.

I would be more concerned with what looks to be an s-trap (on the left).

Thanks Jeffrey - The s trap is on the washer standpipe. Given the amount of non-professional plumbing work in this house, the s trap is the least of their worries LOL

The CI and PVC pipe should have about the same OD if they are the same pipe size. What varies somewhat is the inside diameter …

CI Soil/Waste Pipe:
PVC Soil/Waste Pipe:

That appears to be a 4" CI/PVC x 3" CI/PVC fernco coupling which looks like this …

Have the plumber check that out while he is there … :wink:

Sure appears to me that the CI is 4 inch and the PVC is 3 inch just saying;-):wink: who wants to buy 4 inch PVC its expensive