Welocme to the forum!
You should be able to follow the plumbing, with a bit of imagination. Usually it follows a reasonable route, along walls. If it is above the floor, look under drawers, pull them out look, if under, you should be able to see them laid along the frame at the top of the storage area.
If you have a black tank flush system, you will see the water only when you use it, and, likley the water will pour out, in floods!
That can be a bit more difficult to find, but, it will be up high, has to be highest spot in cold line to effect a vacuum break. I have found them in small access panels in the back of closets, behind refrigerators, under cabinetry, and no where near you would think them to be, so much for sensible aspect!
Not likley you will find a diagram, so drag out your light, and a screwdriver, and go on the hunt!
Let us know what you find!
Back to a 5'er after 4 yrs fulltime.
Pulling with a '14 2500 ram, 6.4 Hemi.
Montana High Country 31RE