Epsom salts have long been thought to have a number of healing properties which is why many people find relief soaking parts or their entire bodies in Epsom salts.
A few of the reported benefits are relief of sore muscles and joints, increased ability to flush toxins, and relief from joint problems.
That being said you should never add Epsom salts to your spa or swim spa.
Here is why:
Salt levels above 1500 ppm can be corrosive in a spa depending on the pH. The recommended level to get the most from Epsom salts is 20,000ppm. Yes you read that correctly. Say you have emptied your spa or swim spa and now only have fresh water in it with no chlorine, you load in your Epsom salts and you will now create a chemical reaction that will attack dissimilar metals. One of the metals will be corroded. This quite often is the spa heater element or parts of the spa pump.
NOTE: Soaking in epsom salts is a good but only for use in your bath tub or foot bath where you drain and change the water with every use.