Backpains,
I go away for a while and you're in trouble already
You have an out building, isn't it near the house, I'd say and let me stress "if you absolutely need to drain the tub", use the heater like someone suggested, and if the house is close enough, they sell a hose system for fish tanks it syphons to the sink and when your done it refills same hose. Phython I think it's called.
To everyone, try to relax a bit, people have bad days all the time, with zero excuses. And some people are just plain rotten. We all know backpains is not one of those so maybe we could cut her a little slack. And if you don't want to hear what everyone thinks (good, bad and indifferent around here, don't ask.
Stay cool people