Epsom's salts was the WONDER DRUG of hospitals back in 1920. Taken internally to flush the bowels and soaked in to relief muscle pains, used in an IV to stop pre=labor, etc., etc., etc.....
It is not plant based, the body sees it as an enemy and thus flushes it out, so I would agree with what the man told you.
Your water system does not make your water safe to drink, ONLY to get cleaner cloths. "IF" it has a changable filter, do it every 30 days at the MAX. For drnking, use a water distiller only.