I don't know if this is possible, but is there a way of measuring the MPS just by measuring the combined chlorine? I know the MPS show up as CC in a DPD test. I'm using mainly MPS in my hot tup right now and doing a chlorine chock every 14 days, so far so good.
I've ordered the Lamotte ColorQ 7 (liquids) to keep track of the water.
If it's possible, what ppm is recommended to have in a hot tub and is there some kind of convert table from CC to MPS?