Re: Drain Fresh Water Tank?
You can use the pump, or disconnect the hose that runs from the tank to the inlet side of the pump. Either method will drain ALMOST all of it. You'll need to keep adding some and draining to get all the old water out.
Once you've got all the old water out of the system, add a half cup of plain bleach to the tank and fill it with fresh water. Run the mixture through all the faucets and let it sit for a day. That'll kill any bacteria in the tank, water heater if you have one, lines and faucets.
Finally, do the whole drain and fill operation again, and do that every couple of weeks so the water stays fresh.
Good luck!