After I remove some concrete to set the p trap for a shower pan, what's a good rough in height for the trap? An inch or two below the bottom of the concrete slab then cut the excess 2" pipe before installing the pan?
Does it depend on make/mfgr of the drain or are all shower drains standard?
It really depends on the pan and the drain assembly you are going to use. I think you'll want the trap deeper than that IF your drain line will support it for some flexibility. If it is that close to the surface, I think you'll really restrict your choices.
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Important note - I'm not a pro
Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013