Calcium buildup in pool

The main causes of calcium buildup in pool interiors is:

  1. High pH in the pool water
  2. Surface has become loose or drummy
  3. Very high calcium hardness
  4. A Calcium nodule has formed inside the surface

Stubborn calcium buildup in pool interior surfaces is often a hard white scale on the pool surface. Calcium is something that many pool owners deal with regularly because it is very hard, stubborn and difficult to remove. Also, because most pool shops don’t know how to remove it (besides draining the pool) they often suggest acid washing. As a result, most pool shops will recommend draining and acid washing your pool to remove the calcium. While this sometimes works, the calcium usually returns soon after the pool water is refilled. Then, your right back to where you started! Worst of all, you have now just wasted $1,200 and a lot of water.

The best way to keep calcium away is to properly maintain the pH and alkalinity of the pool water consistently.

calcium on pool surfaces
Hard calcium formation on Quartz swimming pool surface

Calcium in pool water does not cause calcium spots

Many parts of the country have different calcium levels in their tap water. For this reason, many pools can have high calcium levels in their pool from the beginning. Generally, high calcium levels will not affect your pool surface in the short term if the water is balanced. This is because balanced water helps to keep calcium suspended in the water. In this condition, it will not plate out, or precipitate onto the surface. We have more information about calcium on this page. Finally, if you can bring the calcium back to the right range it will definitely help in the long term.

Reduce hardness in pool water

As with every other aspect of water chemistry, calcium hardness also needs to be in balance to protect your pool surface from calcium formation, stains, or corrosion. Unlike pH and chlorine, the calcium level in most pools does not vary greatly over the seasons, so testing every few months is normally enough. Importantly, high or low calcium hardness can cause white staining on pool surfaces, etching, or discolouration. Remember, the trick is to keep the calcium at the right level and to keep the water balanced.

Calcium hardness reducer

Some inexperienced pool technicians believe that adding a ‘calcium hardness reducer’ will permanently lower the calcium level in the water. This is simply not the case because the calcium isn’t actually physically removed from the water with these treatments. Whats actually happens is that they work by using chemicals to bind up (or capture) the calcium temporarily.  Once the chemical has worn off, then the calcium in simply released and the levels will return to the previous calcium hardness level.

While these treatments do reduce the effects of high calcium in the short term, after 4-6 weeks, the ‘reducer’ chemical is completely neutralized and broken down. A complete waste of time and money. Remember, these products will not remove calcium on pool surfaces.