Getting the schematics is a must. Generally, the low point drains will be under the areas of the water usage, as in shower area, under sink(s), etc. Look under coach for the blue and red lines hanging downward a couple inches or so. Just above them, in a storage bin or very close by will be the valves. Your water pump will be located very close to the fresh water tank. My Chateau 35 has water tank under the bed with an access panel under mattress.
2018 THOR Chateau 35SF
Two Labs, Bugsie & Blondie