If you never got the owner's manual then I have two books I will suggest BUY ONLY ONE
one is called The RV Owner's Handbook
The other is The RV Book (As best I recall)
THey should cover just about everything including a bunch of stuff you do not have.. The major differences between these two books are the name of the book and author and publisher (one is a Woodalls' (Good Sam) publication sold at Camping World.. NO, I forget which).
Now. on your water heater. IF it is "Winterized" then it is likely bypassed. There are three different bypass systems 1,2 and 3 valve
1 valve is a single "3 way" valve. may be labeled "USE/BYPASS" may be unlabled May be in the cold water line just behind the Water heater May be on a panel you access from outside. They can indeed play "Hide the valve" with 'em.
You turn the valve 90 degrees (Generall the water flows in the direction of the valve handle.
on this system the HOT side has a check valve (Which by the way is often a major PITA)
Next: 2 valves.. You have TWO 3-way valves. Now these will often be on what i call the "Back" (Plumbing) side of the water heater.. on in the HOT one in the COLD line.. Same instructions only BOTH valves need to point to the water heater.
Next 3 valve system (What I have) these are usually in back of the water heater as well
Two valves (hot and cold) need to be OPENED and the BYPASS (center) one closed. My Valves have oval shaped handles and when the MAJOR (long) Axis is parallel to the pipe that is open.
NOw. if you have water in your fresh tank turn on the pump. in about 4 minutes open the hot valve. Expect some strange behaviour for 5 miniutes or so. When you get smooth flow it's full.
If you have city water. may not take as long but expect strange behaviour when you open that hot valve.. Nothing wrong with it absolutely normal. just seems strange the first time or two.
Now. There are 3 or rather 2x2 Water heaters
Atwood/Surburan
Manual pilot gas only... DSI Gas/Electric
Instructrions vary depending
On an Atwood you will have two switches inside (Gas/Electric) and if turning on ELECTRIC causes a near instant FAULT light.. There is a RED wire that needs to be connected to the ECO outside.
That's all I'll say for now.
Home was where I park it. but alas the.
2005 Damon Intruder 377 Alas declared a total loss
after a semi "nicked" it. Still have the radios
Kenwood TS-2000, ICOM ID-5100, ID-51A+2, ID-880 REF030C most times