Water smokers...
I had one, never again.
If you're going to actually smoke something, the last thing you want to do is surround it with a lot of water vapor. Smoke doesn't like sticking to wet surfaces.
Anyway... Sorry, I don't have any source for a manual, but you may try looking at the manual for the Brinkman electric water smoker to maybe get some basic guidelines.
I never thought about the water vapor and smoke, I thought it made for a good hot smoke. I might get a taste surprise when I start using the electric smoker.
Figured there might some manual in all the stuff you have discovered in the basement of your Grandparent's house.
Charby
He got a heavy duty dimmer switch and wired it in there, making the burner output adjustable. That was a great smoker after the modification!
I was already thinking that and put a couple thermometers one at the bottom and one at the top through the sides.
C