MPS is a non-chlorine oxidizer (potassium monopersulfate) that is used to help control bather waste in addition to your normal chlorine use. Organic combined chloramines, those chlorinated compounds generated from the oxidation of urea and creatinine (components of sweat and urine), can remain in hot tubs and build up over long periods of time or heavy tub use (high bather loads with frequent bathing). MPS helps to destroy those compounds before chlorine reacts with them.
The downsides of MPS are that it will interfere with the FAS-DPD testing in the short term (24-48 hours after dosing), it is acidic which will lower TA & pH, AND it will cause the build up of sulfates in your hot tub water which can lead to accelerated corrosion of the heater. You can purcahse an additional test reagent to help remove and account for the MPS interference.
I would say this - don't use the MPS just yet. Simply run your tub on chlorine and, if you feel like it, shock the tub once per week with chlorine. Keep an eye on the CCs and let the tub breath every now & again. See how the water reacts. It's probably just cheaepr and easier to drain the tub every 3-4 months once the CCs start to build up rather than use MPS.
Installing a UV sterilizer would be the better option since UV light acts as a potent oxidizer. However, most tubs don't allow for easy installation of UV lamps, so it's not usually an option unless the tub was originally spec'd to have one.
