calcium in swimming pool

Calcium buildup in pool

The main causes of calcium buildup in pool interiors are:

  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 interiors 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 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.  If everyone did this then there would be no calcium buildup in pool surfaces at all.

FAQ- Calcium Hardness

What level should my calcium be?

For pebble, quartz and glass bead pools the suggested calcium hardness is 200-250ppm.  Suggested levels for fibreglass pools vary depending on the manufacturer?

Does high calcium cause calcium spots ?

As a rule, there is no link between calcium levels and calcium buildup in pool interiors.  Calcium stains and spots are usually caused from poor water balance.

Do calcium Hardness reducers work ?

In our experience, calcium hardness reducers do reduce calcium levels in the short term.  However, over time the calcium hardness returns to the old levels.

does calcium effect water quality ?

Calcium rich water is called ‘hard’ water.  This is because the calcium content is very high.  Low calcium water is called ‘soft’ water which feels much nicer to swim in.

How do I increase calcium hardness?

Calcium hardness is increased by adding calcium chlorite from the pool shop.  It is very cheap to buy and easy to add.  Your pool shop will help you know how much you need.

How do I reduce calcium hardness ?

To reduce calcium hardness permanently is best to partially drain the pool water and refill it.  This process removes high calcium water and replaces it with low calcium water.

Calcium hardness reducer

Some inexperienced pool technicians believe that adding a ‘calcium hardness reducer’ will permanently remove calcium buildup in pool surfaces. 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 buildup in pool surfaces.