Calcium in pool water

Calcium the Good and Bad

Calcium hardness is the measure of dissolved calcium found in your pool. If these levels are not right, then it can lead to damage to your pool and equipment.
Calcium levels are sometimes overlooked when testing but it is an essential element of water balance and should not be overlooked so should be tested regularly as well.

Calcium hardness in your pool or spa is measured as calcium carbonate which is not very soluble and can easily drop out of solution especially when water temperatures increase or poor water balance.
This can be noticeable by having calcium deposits form on surfaces of equipment or your pool and spa.

The ideal levels are between 80ppm and 400ppm, 200 being ideal, i also recommend that the warmer your water temperature, the lower the level you should have to help eliminate the calcium carbonate from forming on surfaces.

Low calcium hardness levels can result in corrosive water.
The surfaces can be affected, tile grouting can soften and eroding of equipment even leading to rusting will eventuate with the aggressive unbalanced water.
Staining can also be a problem with low calcium, though using course salt with iron or metals present is the main instigator of pool staining.

To correct low calcium levels, just add the required amount for your volume of pool or spa water and increase this but stay at the ideal range for optimum water balancing.

High calcium hardness levels can result in scale formation on pool surfaces and equipment. As the below picture can demonstrate. This a picture of a pool cell from a chlorinator and cell combination which converts salt or minerals in your pool to chlorine.

As you can see the cell has been covered in calcium carbonate, once this happens the cell will not be able to operate correctly, thus your chlorine levels will be low or non existant leading to other problems.
To correct this you must clean off the calcium carbonate.

The best way to clean it is with either a dedicated cell cleaner solution from your pool shop or you can use Hydrochloric Acid and Water in a bucket. Dilute One part Acid to 10 Parts Water. Soak the cell in it, but do not submerse any wiring only the plates.
The calcium carbonate will fizz and come off the cell, the time duration will be dependent on the severity of calcium carbonate deposited on your cell. Leave until clean then rinse off and replace back into it's housing.

Other associated problems with high calcium hardness levels will be:

• Cloudiness of pool water
• Scale forming on equipment
• Clogging of pool filters
• Clogging of heater elements
• Possible eye and skin irritations
• Scale forming on pool and spa surfaces

Along with correct water balance, adding water softeners may aid in a reduction of scale formation or carefully pouring Hydrochloric Acid on any surface formation can remove it as well.

Other tips are when building a new concrete or tiled pool it is essential to monitor your calcium levels weekly as this is quickly absorbed  by the concrete itself. If a good balance is not keep at these early stages it may lead to leaching of calcium from the lime in the cement onto the pool surface, tiles and pebble will fall off and calcium nodes will form on surfaces as well.

If your calcium levels are constantly falling this may also be an indication of a leak in your pool. 

Next we will discuss a few of the other elements essential to pool water quality.

The Pool Professor

Hacienda Na Xamena Hotel in Ibiza, Spain