[NH_Bulldog]

I would guess that the backflow fitting on the hot outlet is either missing or malfunctioning. It is possible that when the tank was replaced, the fitting was left on the old tank and/or not installed in the new one. You can either add/replace the backflow fitting or convert to a three valve system.

As far as pumping antifreeze, you can pump direct from the bottle and use 2 gallons or less for the entire camper (We have a toilet, tub/shower, bath sink, kitchen sink, outside kitchen and outside shower). As a short-term solution, I bought a spare quick connect fitting for the pump, and added a 2’ piece of hose. I pull the quick fitting on the suction side of the pump, snap in my new short suction hose and pump right from the jug, then remove and reconnect the tank suction line. In the spring, I am going to add a tee valve into the tank suction line and permanently install the bottle draw line.

Pump off, all faucets and low point drains opened. Fresh water tank drained and valve left open. Water heater drained and bypass set. Air compressor to (gently) blow water out of lines, including black tank rinse line. Grey and black tanks rinsed, drained and valves closed. Low point drains closed to retain antifreeze. Close all faucets, connect antifreeze bottle draw and turn on pump. Starting at faucet furthest away, go to each faucet and open until you get antifreeze, hot then cold. Change bottle as needed. Flush toilet a few times leaving antifreeze in bowl. Now you have antifreeze in all plumbing lines, faucets, drains, traps, grey tank, black tank and pump.