I don't know about any schematics but the process is simple. Fresh water leaves the fresh water tank and fed by gravity to the water pump. The water pump pressurizes the water and then off to the water heater. Due to weight balance the water heater would normally be on the opposite side of the fresh water tank. At least that's the case on my T1350
At the water heater you should see two pipes usually plastic type. There should be a "TEE" fitting at the bottom of the tank. This TEE fitting allows cold fresh water to EITHER pass through and continue on to your cold water faucets and ALSO allow fresh water to enter the hot water heater. The heated water will exit out of the top of the heater to its hot water faucets.
Added to the mix is the inlet for the fresh city water service. This too would also TEE into the mix. Open up all your cupboard doors below and map things out the way you think they should work.
When I winterized mine I bypassed my hot water tank and just plain emptied it. There is a master drain plug at the bottom and access from outside of the trailer via that trap door. Mine is a plastic plug and rather large. Obviously for draining the drain-plug is on the bottom so make sure you have the fitting on the opposite and inside top of the tank open as well, so that, the tank has air to breath when draining. I just left my water tank empty and never filled it with antifreeze. BUT, I REALLY MADE SURE IT WAS EMPTY !!!!!
When you use antifreeze for trailers make sure you use RV antifreeze (the pink stuff) It's non-toxic.
Using car antifreeze could kill you if the ratio is done by an overzealous person.
I usually empty my fresh water and remove the feed pipe from the fresh water tank. Then I run a line from that gallon of anti-freeze and watch for a pink water running our of each tap (hot and cold and also the pooper machine) I'll run a wee bit more than needed and that assures me that I'll have antifreeze in the black and gray water holding tanks.
I use a visual to make sure there is NO water in the fresh water tank.
This year my wife noticed a garbage type odor in the trailer. It took a while but I figured out that this odor only took place when she ran a tap. The old pink antifreeze kind a stinks after a while. I guess when I purged there must have been some residual. hence is why they recommend NON TOXIC.
We never ever use or recommend the trailer water for drinking. Washing dishes and hands and that pooper is what we using it for. For drinking we pack a couple of cases on bottle water.
Water weighs 10LBs per gallon
BTW, Anything I'm not 100% sure of, I will tag it. I'll use a piece of painter's masking tape and write on the tape what or where each pipe goes. That way if you think you might mess up , you can always return everything to its original position. I have a good memory but it's short