Goto the nearest store will pool supplies.
Get spa minus. Get some gloves and mix a bunch with water, pour into the tank, let it sit. It's ph reducer, it's really cheap and it's easy to work with, usually pellet form. You can get it just about any hardware store probably.
If I remember right though when it mixes with water you get sulphuric acid.
Then you can neutralize it and put it down the sink