I want to build an in-ground hot tub. I need the plans on what I need for plumbing? Not the kind of material, but the layout and such. Which lines to what and just how it should be layed out.

New pool built last fall, started up and closed by pool company. Same company (that built the pool) opened it up 9 days ago and cleaned it last saturday. I didn't notice this mark until yesterday, it is in the shallow end just off the bottom step, and it looks like a 1.5" long and narrow rust stain on the floor. Tried lightly scrubbing it with the pool brush, but did nothing. My wife thought maybe a nail or screw was sittin gin there over the winter when they covered it, resulting in a rust stain. I figured I would have noticed that. Pool is chemically balanced and filter has been running 6-8 hrs per day since opening. Any ideas? I will wait for some responses, then contact the pool co. and have them come out and look at it. Thanks.