onetaste

UPDATE: I have been using Magnesium Chloride (actually magnesium hexachloride flakes, my limited understanding of chemistry suggests this is effectively the same thing once dissolved) for 10 months in my new spa now and we are extremely pleased with the results. I put in 750g in a 750 litre hot tub. This is nowhere near the concentration you would use in a hot bath (eg 300g in a 60 litre bath) however it has made the water feel very soft and we get out of the spa with the skin feeling great. FYI I also use hydrogen peroxide at >100ppm to sanitise with MPS every week or two. My wife and I really like the magnesium. We have noticed some grey "scum" as a result, mentioned in a post above, which is a few grey bubbles that hang around a bit longer than usual, but these dissolve back into the water 30-60 secs after the blower is turned off, there is no scum on the water line. I have been told by a hot tub retailer that recommends Mg in his tubs that it should not harm the hot tub, but it will damage the pump seals over time and these will need replacing.

bump I would like to use Magnesium Sulphate to replace Calcium just for the purpose of maintaining correct water hardness (not to get the spa to therapeutic levels of Mg). Is this possible, does anyone have any experience with this?

In that case, can't we run Spa Flush for the required period and then super shock after that in the same water? I am on rain water only and have very limited supply.

I would like to use Magnesium Sulphate to replace Calcium just for the purpose of maintaining correct water hardness (not to get the spa to therapeutic levels of Mg). Is this possible, does anyone have any experience with this?