Stop Pool Plaster Etching & Surface Damage

Pool Plaster Etching and Surface Damage

Objective 

This guide explains why pool plaster becomes rough, pitted, or "etched" over time, and provides the exact water chemistry adjustments required to halt the damage and protect your investment.

The "Universal Solvent" and Your Plaster 

If your once-smooth pool plaster is starting to feel like rough sandpaper, your water is sending you a critical warning. Water is known in chemistry as the "universal solvent"—it is constantly seeking thermodynamic equilibrium. If your pool water lacks the proper amount of minerals (specifically calcium and alkalinity), it becomes aggressive and "hungry." To satisfy its appetite, the water will literally dissolve and extract the calcium carbonate right out of your plaster walls. This process is called etching. By balancing your water properly, you "feed" the water the minerals it needs so it stops eating your pool.

Step-by-Step Instructions: Stopping Corrosive Water

  1. Test Your Current Chemistry: Using a reliable drop-test kit, check your current pH, Total Alkalinity, and Calcium Hardness levels.

  2. Identify the Imbalance: Etching almost always occurs when the pH drops too low (below 7.2) or when the Calcium Hardness is drastically under the recommended minimum of 200 ppm.

  3. Correct Your Alkalinity First: Do not immediately throw pH increaser into the pool. First, ensure your Total Alkalinity is within the stable Hamilton Index™ range of 60–90 ppm.

  4. Allow the pH to Rise naturally: Stop fighting the water! Once your alkalinity is set, allow your pH to naturally drift up to its equilibrium point of 7.8 to 8.0. A stable pH of 8.0 is completely non-corrosive and will immediately stop the water from etching your plaster.

  5. Adjust Calcium Hardness: If your Calcium Hardness is below 200 ppm, purchase a Calcium Hardness Increaser. Broadcast it evenly into the deep end of the pool while the pump is running to satisfy the water's mineral demand.

Troubleshooting Note: The "Spot Etching" Myth

If you only see small, isolated gray spots of rough plaster rather than widespread roughness, you may be experiencing what the industry calls "spot etching." This is often a defect in the original plaster application (improper troweling or curing), which is unfortunately exacerbated by aggressive water chemistry. Keeping your pH near 8.0 prevents this weakness from degrading further.

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