I think Larry has given a pretty good summary of the situation.
I have had three 2720SL TMs (more recently called 2720QS - same trailer, updated model name). Mine were a 2002 model, a 2006 model, and my current 2020 model. The TrailManor web site says that the 2922 is the same as the 2720 except that it has been lengthened by 2 feet to accommodate a king size bed. Specifically it says:
"The TrailManor 2922 Series fits an important place in our product line — three new trailers that offer the same highly popular floorplans of our 2720 models — but with a KING sized bed."
To my knowledge, the water heater has always been under the sink, and during my 20 years of moderating this forum, I've not seen a mention of the heater anywhere else for any model. If your manual says something else, perhaps you would copy that statement out for us.
Again, as Larry says, the fresh water
tank is in different places and different sizes on different models. There are references to 11 gallons, 20 gallons, and 40 gallon tanks.
As for the ON-OFF switching for the water heater, this can easily be confusing. The water heater can heat water using two different sources of heat - gas and electricity. The gas switch is on the apron in front of the sink. There is a rocker switch and a small red light beside it. When you turn the switch on, the red light will come on for a few seconds, then will turn off. This reflects the operation of automatically lighting the gas burner. The operation takes several seconds, during which the light is on to signify "Igniting in progress". Then, when the burner is lit, the red light goes out and the heater begins normal operation. No, there is no persistent ON light, any more than there is one on your home water heater.
Just to make things confusing, the switch to turn electric heating on and off is outside the trailer, on the body of the heater behind the louvered panel. Take a look at the blue arrow in this picture
https://www.trailmanorowners.com/for...&pictureid=447.
Incidentally, the manual says that it is OK to turn on both the electric and the gas heating elements at the same time. As the manual also says, neither the gas or electric heating element should be turned on until the water heater is filled with water.
I agree that the manual is not exactly a work of fine literature. But it has been reasonably stable, because the design of the TM has been reasonably stable. If you find other discrepancies, please inquire about them here. We will be glad to help straighten things out.
Bill