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Calcium scale is different then [[Waterline Scale Removal|waterline scale on tiles]], evaporative scale on surfaces outside of the water, [[Efflorescence|efflorescence]], or [https://www.troublefreepool.com/threads/calcium-nodules-in-pools.66499/ calcium nodules]. | Calcium scale is different then [[Waterline Scale Removal|waterline scale on tiles]], evaporative scale on surfaces outside of the water, [[Efflorescence|efflorescence]], or [https://www.troublefreepool.com/threads/calcium-nodules-in-pools.66499/ calcium nodules]. | ||
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| + | ==What Causes Calcium Scale== | ||
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| + | If there are too many calcium and carbonate ions in the water, then they will combine and form calcium carbonate scale when pH is high. We measure the calcium in the water and the carbonate as TA in the water. We then use PoolMath to calculate the waters Calcium Scaling Index (CSI) using pH, CH and TA to tell us how likely scale will form. A positive CSI above +0.6 indicates there is a risk of scale formation. | ||
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| + | Scale does not form overnight with a high CSI. It takes many weeks of the high CSI water to have the calcium and carbonate ions to combine and form scale deposited on the pool surface. | ||
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| + | Calcium scale is often discovered when a pool or spa is opened after being closed for the winter. While the pool is closed the pH will tend to rise to reach equilibrium with the TA. With high TA pH can rise into the high 8's or 9. Water left still for a few months with high pH, TA and CH can for scale on the surfaces which will feel rough. | ||
Revision as of 20:46, 14 April 2024
Calcium Scale
Calcium scale forms on pool surfaces due to very hard and out-of-balance pool water. Calcium scale is usually uniform and covers both plaster and pebbles in a pool. Calcium scale usually feels rough, like sandpaper, on the pool surfaces.
Calcium scale can occur on plaster, vinyl liner, or fiberglass pool surfaces.
Calcium scale is normally from calcium carbonate but can be from calcium sulfate (CaSO4). Aqua Magazine:The Mystery of the Pointed Crystals describes a calcium sulfate scale situation. Orenda Understanding Calcium Sulfate Scale Crystals further describes calcium sulfate scaling and solutions for it.
Calcium phosphate can also form scale and we rarely see that in pools.
It is important to identify the type of calcium scaling to know how to treat it. Calcium carbonate will fizz up in acid, while the other two either don't react at all or just slowly dissolve. By testing the calcium level and calculating the waters CSI as well as testing for sulfates and phosphates you can identify which chemicals are unusually high.
Calcium scale is different then waterline scale on tiles, evaporative scale on surfaces outside of the water, efflorescence, or calcium nodules.
What Causes Calcium Scale
If there are too many calcium and carbonate ions in the water, then they will combine and form calcium carbonate scale when pH is high. We measure the calcium in the water and the carbonate as TA in the water. We then use PoolMath to calculate the waters Calcium Scaling Index (CSI) using pH, CH and TA to tell us how likely scale will form. A positive CSI above +0.6 indicates there is a risk of scale formation.
Scale does not form overnight with a high CSI. It takes many weeks of the high CSI water to have the calcium and carbonate ions to combine and form scale deposited on the pool surface.
Calcium scale is often discovered when a pool or spa is opened after being closed for the winter. While the pool is closed the pH will tend to rise to reach equilibrium with the TA. With high TA pH can rise into the high 8's or 9. Water left still for a few months with high pH, TA and CH can for scale on the surfaces which will feel rough.
