The OP said it has antifreeze in it, and wanted to know how to remove it.
Absolutely do not open the valves to the hot water tank until all traces of antifreeze have disappeared from your taps. You should collect the antifreeze from the taps until it starts to look watery when flushing and save it for putting into your black tank and grey tank next time you need to winterize. It is just slightly diluted and still very useful. Mark the containers as diluted though.
Once you have put water through the street connection and drained the system, put some water into the fresh tank and run the pump so antifreeze goes out of there too. You must remember to do each water outlet and do it with the cold tap separate from the hot tap and not both together.
When you cannot taste antifreeze in the tap water, then take the hot water tank off bypass and let some water into the hot tank and let it run out the drain for a few gallons. Then fill the tank and run some water through the tank and out a hot tap.
There is lots to learn, and lots of mistakes to be made. My worst was pouring antifreeze into the hot water tank and out onto the ground out the open plug because of a stuck open hot line check valve, and the next was pressing the check valve head on the street water hose inlet while the system was pressurized. That buggered the check valve and sprayed all over the place too.