What is calcium hardness?

Pools need calcium just like us. Calcium naturally occurs in water at anywhere between 1-100ppm depending on the source. Calcium in our bodies makes our bones stronger while calcium in the pool can make the water hard or soft, which is where the term calcium hardness comes from. The higher the amount of calcium in the pool, the ‘harder’ the pool becomes. Calcium can be added to your pool in a few ways: water source, some chlorine and adding it directly. Although it seems we are always encouraged to drink milk for strong bones, too much (and too little) calcium in your pool can create a few issues.  

Why do I need calcium hardness?

Having the right amount of calcium hardness protects your pool and your family. We recommend your pool calcium levels to be around 100-150ppm. If your pool does not have enough calcium, it will attempt to draw calcium out of the walls, from the grouting in a tiled pool or in extreme cases from our bodies such as our nails and teeth. It can also corrode your equipment, pipes and fittings and also makes surfaces slippery. At the other end of the scale, too much calcium can leave your pool looking milky or cloudy, hurt swimmers eyes and even build up on equipment causing corrosion.

How do I treat high calcium hardness levels?

The most effective way to reduce calcium hardness is by draining the pool and refilling it. It can be tiresome and requires time and patience. Depending on how high the calcium readings are, we recommend draining around a quarter of the pool and retesting the water chemistry. This will tell us if we need to continue with diluting the calcium or if we have reached optimal calcium levels. We can also rebalance the water when calcium levels are closer to optimal.  

How do I prevent high calcium hardness levels?

  • Test water chemistry often. When calcium hardness begins to increase we can investigate why and prevent it from increasing
  • If using a powder chlorine, swap between chlorine that has calcium and one that doesn’t, such as stabilised chlorine. By swapping between two types you avoid building one up too high