500g Relax Spa Hardness Plus Your spa water needs to contain a Calcium Hardness of between 200 parts per million (ppm) and 300 ppm Low Calcium (soft water) will cause expensive damage to your spa equipment This is particularly important if your tap water is soft water (low in Calcium) Test the Calcium Hardness immediately after you have drained and refilled your spa water and at least once per week
