I'm installing a basement shower. When the house was built 2 years ago, it was pre-roughed, with a plastic cover over the hole where the drain will be. I was surprised after opening up and removing some dirt that the 2" horizontal drain line is so deep - it is 12-1/4 inches from the top of the slab to the top of the line. If I come straight down from the drain in the shower pan to a p-trap on the horizontal drain line, it will be over 12" drop. Is that OK, or is there some limit to how far down the trap is from the pan?

No problem Billy,
As long as the trap is properly vented you may make the drop from the drain,( The tailpiece) as long as you want. It's the distance from the trap to the vent that's critical. Good luck, Tom

I wouldn't think so. Washer drains may be 3 feet down to the trap. The trap allows water to go down, but not sewer gas to come up. It needs to be before any tee.

Thanks for the replies!