Ideal Calcium Hardness Range: 150-400
Testing Calcium Hardness:
We recommend taking a sample of your hot tub water to a dealer test station or using an advanced test kit.
What is Calcium Hardness?
Calcium hardness is the measure of how hard or soft your hot tub water is, and measures the amount of dissolved calcium and magnesium. Just like pH and Total Alkalinity, it’s important to keep the calcium hardness balanced to prevent your hot tub water from becoming corrosive or scaling. However, before you attempt to balance your hot tub’s calcium hardness level, first make sure your Total Alkalinity level is balanced, then the pH and lastly calcium hardness. The ideal range for calcium hardness is 150-400 ppm (parts per million) for hot tubs. To determine if your hot tub is properly balanced use our Langelier Saturation Index (LSI) calculator.
Low Calcium Hardness
When hot tub water becomes too soft (i.e. its calcium hardness drops below 150 ppm) it becomes corrosive. If you don’t manually add calcium or magnesium back into the hot tub, the water will begin to take what it needs from any part of your hot tub and equipment that contains stone, concrete, metal, grout, etc. Problems often associated with low calcium hardness include:
- Eroding of tile grouting and delaminating of plaster surfaces
- Etching or pitting of hot tub decks/stairs or stone and concrete surfaces surrounding your hot tub. Corrosion of metal parts (i.e. pipes, heating elements, pump seals, internal parts on gas fire heaters, etc.)
- Pitting of hot tub flooring and walls
Once damage from soft water occurs, there’s no way to undo it. It’s imperative not to let your hot tub’s calcium hardness dip too far below 150ppm.
How to Raise Calcium Hardness in Your Hot Tub
If your hot tub’s calcium hardness level drops below the recommended 150 ppm the easiest and most common way to raise calcium hardness is by adding a calcium hardness increaser such as calcium chloride to your hot tub.
High Calcium Hardness
Similarly to when the hot tub’s pH level is too high, when a hot tub’s calcium hardness level is too high it becomes basic and over saturated with dissolved particles including calcium. Over time, the water will become cloudy and the excess amount of dissolved particles in the hot tub will cause the water to scale in and around your equipment, possibly clogging and blocking the flow of water in and out of the hot tub, which can damage your hot tub equipment.
How to Lower Calcium Hardness in Your Hot Tub
There is really only one way to lower your hot tub’s high calcium hardness level and that is to partially or completely drain your hot tub water and replace it with fresh water.
FROG® Fresh Mineral Water is softer because minerals condition the water for softness so it’s easier on you and your pool or hot tub with no faded suits or smelly odors.
FROG’s Nutty Professor on Calcium Hardness