Calcium Hardness

Sometimes referred to as "total hardness", calcium hardness is a measurement of minerals in your water including calcium and magnesium. You do want your water to have some level of hardness. If the water does not have enough calcium, the water will draw from other minerals, including copper, aluminum and iron, (e.g., heating elements, pump seals, and internal parts on gas fired heaters). This will result in equipment corrosion. If there is too much hardness, you will see scale formation on the spa's interior and the water will take on a cloudy appearance. Because of this, it is recommended that you fill your spa with water from a softener instead of tap water.

So what should the calcium reading be? Between 100- 250 PPM's for acrylic finish, and 250-450 PPM's for plaster finish. Let's look at some potential problems if it goes unchecked.

Hardness too Low

Hardness too High

Deterioration of Metal

Components in Spa Equipment

Scale Formation On Surfaces
Unwanted foam Cloudy water


If your water is high in calcium there is no known way to lower it using chemicals. Using Spa Defender gives the best preventive maintenance against scale formation. Also, if your water is high in calcium this is where you may want to use water that is treated by a softener to fill your spa. In many cases you will find a low calcium reading that can be adjusted by using Calcium Booster. To make any adjustments to calcium hardness you will need a test kit or test strips.

Well that's all! All the really important stuff anyway. There are other chemicals available that will help keep your water clean, clear and free from oily scum. These can be found in the Chemicals section.

Remember, test your water regularly, but most of all, enjoy your spa!