second story bathroom additions

[mrz]

When adding a second story to a single story ranch, can the 2 new
upstairs bathrooms share the same sewerline?

[Rich]

They can if it's sized correctly.. I'm thinking 4" would do it.

[bkrahmer]

3" is probably more than enough. Here is an online code reference: http://www.metrokc.gov/health/plumbing/unitvalues.htm It's for Seattle, but pretty much mirrors UPC. Two normal bath, i.e. lav, tub/shower, toilet would be 12 fixture units. 3" takes up to 35 fixture units horizontal and 48 vertical.

[Rich]

I guess I'm too used to commercial construction and my current project. :)