Chem Geek -
To clarify: I have no swimming pool, just the hot tub. Water heater is tankless so no help there. There is no salt water system, but it does have an ozenator type system. Temperature is kept at 80 to reduce cost, discourage swimmers, and reduce growth of nasties. No one uses the hot tub at all. It is basically patio eye candy that came with the house. I thought it might as well serve a purpose.
I think hydrochloric acid should also work, but not sure where to get food or pharmaceutical grade low molar.
Or maybe I should just use the vinegar.
Thoughts?