A proper test kit should contain a calcium hardness test mechanism. Calcium hardness tests were once just for swimming pools–but we’ve discovered that it is also important for your backyard hot tub. The reason to test for calcium hardness in pool water is because a low calcium hardness reading is destructive to the pool’s plaster. (Priced plaster replacement lately? Think second mortgage to pay for the replacement.)
All tap water has variable calcium hardness readings. In that same seam, low calcium hardness in a hot tub is not only corrosive, but also interferes with disinfection, and low calcium hardness can also cause your water to become foamy.
Spa and pool owners often think that they have a lot of minerals in their water and equate that to calcium hardness. WRONG. Calcium hardness is a different measurement apart from total hardness (and that also has little to do with TDS) .
So, the reason I wanted a calcium hardness reading on this sludgy spa was: 1) to determine the effectiveness of the disinfectant and; 2) to determine if this was adding to the ‘green sludge’ disaster–in that it could cause the water to foam.
Maintaining your spa’s water can be like maintaining your own skeletal health, but this low-calcium hardness business can destroy your spa or pool’s skeletal well-being. If your calcium hardness reading is below 250 ppms, then prepare for funky water, and a visit from your spa’s doctor for an expensive repair to the heater, pump seals and possibly more.
Raise calcium hardness with calcium chloride. You can pick this up at your local pool and spa store.