Do not put pink stuff in your fresh water tank and pump from there. In all the best efforts, there is still some water in the bottom of the tank and it will dilute the pink stuff (not good).
Second, you do not want pink-stuff in your water heater. It will take at least 6 gallons to fill it before the hot water will pump to the rest of camper. It needs to be by-passed. Remove the screws and panel. There's no short cut here.
More than likely, you'll have only 1 valve to switch. There are in-line check-valves that will prevent the water from back-feeding into the water heater once this is flipped. If you have 3 valves, set each one in the opposite setting from where they are now.
More than likely you'll need to get an adapter to pump the pink stuff from your on-board water pump. You removed the intake line side on the pump and replace it with a hose and connection that goes into the pink-stuff gallon jug.
You then simply flip your water pump switch on, let the pump suck the pink stuff from the bottle until the water pump shuts off because the system has reached its pressure.
Then go to each faucet, cold then hot (not both at the same time) until pink stuff comes out of the faucet. When you start sucking air, you'll need to open a new gallon of pink-stuff until all your faucets are done. Remember, bathroom, kitchen, toilet, and outside faucets or outside shower.
Also, remember to let some drain down the bathtub/shower drain, the kitchen sink drains (both sides) and bathroom sink drain so the pink-stuff fillls the p-traps. If you have normal water in them without draining or replacing with pink-stuff, they could freeze and crack. I had this happen to the bathroom sink last year. Easy fix, since it's all standard plumbing parts, but still an aggravation having to do it.
Good luck.
