John, you look inside your rig, "exactly" opposite of where you see the water heater on the outside. That is where you will find the by pass and all the valves.
Like Stan said, you might have to take a panel off, but it's there.
I see you have a rear kitchen. So do we.
My water heater is located on the curb side, back corner. The kitchen sink is in that back corner, and the water heater is right beneath it, along with all the valves. If I remember right, when we got it there was a panel screwed in place right behind the cabinet door beneath the sink. I took the panel out and threw it away. No reason for it to be there.