Ok, I realized I don't even need to heat the water here in Southern AZ in the summer, it's so dang hot that the tap water temp is quite comfortable. So that eliminates the heating problem. I still don't want to leave any standing water, so that means refilling each time I use the soaking tub. Local water rates are around $4 per 100 cubic feet (1 CCF) (1 CCF = 748 Gallons). So say I wanted to limit the water cost to $20/mo, that would mean using about 5 CCF or 3740 gallons. And if I refill 10 times per month, that would allow 374 gallons per use -- that's a pretty dang large soaking tub.
Now, I just have to find something that's comfortable, the right size, and not too expensive. I could get a cheap fiberglass tub but I'm thinking maybe a stock tank pool is the cheapest and easiest (and probably do the best outside in the sun). Found an article about it here -
https://www.countryliving.com/life/a43074/stock-tank-pools/Can get a 70 gallon tank for ~$130 on amazon (
https://www.amazon.com/Behlen-Country-ST214-Galvanized-Approximately/dp/B003B6HHEW). That'd probably work ok, but now I'm getting greedy and thinking I want something larger. Looks like Behlen makes a 6′ Galvanized Round Tank (approx. 389 gal.), so I might try to price that. I'd like to put it in ground but then I'd have to install some kind of pump to empty it right?
Anybody ever used these stock tanks as a mini pool/soaking tub before?