Calcium buildup, commonly known as scaling, occurs when mineral deposits, primarily calcium carbonate, form on pool surfaces and equipment. Scaling is not merely an aesthetic issue; it can reduce water flow by clogging filters and plumbing, decrease heater efficiency, and damage the pool’s surface finishes over time. Addressing this problem requires understanding the underlying water chemistry that causes the deposits to form.
Understanding Scale Formation
Scaling is fundamentally a water chemistry problem indicating the pool water is oversaturated with calcium carbonate. This oversaturation is predicted using the Langelier Saturation Index (LSI), a calculated value incorporating several chemical and physical factors. A high LSI value, typically above +0.3, signals that the water is actively seeking to shed excess minerals by depositing them as scale.
The three primary chemical factors contributing to a high LSI are elevated pH, high Total Alkalinity (TA), and excessive Calcium Hardness (CH). When the pH rises above the ideal range of 7.2 to 7.6, calcium solubility decreases significantly. High TA (ideally 80 to 120 ppm) acts as a buffer that drives the pH upward, further promoting scaling. High Calcium Hardness, especially levels above 400 ppm, provides the raw material for the deposits.
Warmer water temperatures contribute to scale formation by making calcium less soluble, which is why scaling is often more pronounced in heated pools or during hot weather. Evaporation further compounds the issue because it removes pure water while leaving concentrated minerals behind. The combination of these factors creates the environment for calcium to precipitate out and solidify on surfaces.
Manual Removal Techniques
Physical removal of scale is a practical first step, particularly for deposits visible at the waterline or on accessible surfaces. For hard surfaces like ceramic tile, concrete, or plaster, a pumice stone is an effective abrasive tool. It is necessary to keep both the pumice stone and the surface constantly wet during scrubbing to prevent scratching delicate finishes.
Specialized scale brushes, sometimes called stain erasers, are safe for use on softer materials like vinyl liners and fiberglass that a pumice stone would damage. For heavy deposits, a cautious approach involves using a plastic putty knife or a razor blade to gently chip away the bulk of the scale before scrubbing. This initial physical removal makes subsequent chemical or abrasive cleaning more manageable.
For severe buildup on tile lines, professional services often employ bead blasting, which uses fine, high-pressure media like magnesium sulfate to safely strip away the deposits. This method avoids the abrasiveness of traditional sandblasting, which can damage grout. When dealing with waterline scale, it is helpful to temporarily lower the pool’s water level to access the entire affected area easily and keep it dry while working.
Chemical Treatment Options
Chemical treatments work by either dissolving calcium deposits or binding to the mineral ions to lift them from the surface. Scale removers are specialized products, often referred to as sequestering agents, which contain chemicals that form a strong bond with calcium. When applied in high concentrations, these agents break down existing scale and keep the calcium dissolved in the water, allowing removal by the filter system.
For extensive scaling on concrete or plaster pools, an acid wash may be necessary, typically requiring the pool to be drained completely. This process involves carefully applying a diluted solution of muriatic acid to the surface to dissolve the calcium carbonate layer. Due to the corrosive nature of muriatic acid, safety precautions are mandatory, including wearing gloves, goggles, and proper ventilation. This procedure is often best left to a professional.
A less aggressive chemical approach involves controlled adjustment of the water chemistry to dissolve the scale gradually. By carefully lowering the pool’s pH into a slightly aggressive range (7.0 to 7.2), the water’s tendency to dissolve calcium increases. This subtle chemical imbalance can slowly erode the scale over days or weeks, particularly when combined with frequent brushing, but must be managed closely to avoid damaging the pool surface.
Long-Term Prevention Strategies
Preventing future scale formation centers on maintaining consistently balanced water chemistry, especially by controlling the LSI. Routine testing of pH and Calcium Hardness levels is the most effective preventative measure. The pH should be maintained in the range of 7.4 to 7.6 to ensure calcium remains soluble without causing discomfort to swimmers or reducing chlorine effectiveness.
Total Alkalinity should be kept within its target range, as it directly influences the stability of the pH level. For pools in areas with naturally high Calcium Hardness, a concentration between 200 and 400 ppm is the ideal balance point. Continuous application of a quality sequestering agent is a proactive step, as it binds to minerals before they can precipitate out of solution.
Using a non-calcium-based shock, such as lithium or non-chlorine shock, prevents unnecessary calcium additions to the water. Reducing water loss through evaporation, perhaps by using a pool cover, minimizes the concentration of dissolved minerals left behind. Consistent adherence to these balanced water parameters will reduce the risk of future scaling.