I'm pretty comfortable maintaining my spa chemistry with generic chemicals and my Taylor Tech. K-2000 . I am a bit frustrated maintaining the balance between TA and pH but kind of expect it in 211 gallons.
A kilogram of MPS costs $25 here. It may be my most expensive chemical by mass, per dose and per time. My dealer's guidance was "a cap full after every soak". A cap full is ~2oz, ~$1.50.
Is there an objective test for MPS addition rate, please?