x2 on it being antifreeze. It's non-toxic (at least in modest quantities), but not very pleasant.
I'd suggest draining the fresh water tank and hooking the hose up for city water usage (not using the tank) and flushing out the plumbing. It will go a lot faster if you drain the water heater and bypass it to flush the plumbing system, and then un-bypass and refill it (after putting the drain plug back, of course). Be sure that you don't turn the water heater on when it's not full of water, whether on electric or gas heat if you have both. If you don't empty the tanks, it will take a very very long time of adding and removing water from them to get the antifreeze diluted enough to be unnoticeable.
