— Local service
Calcium carbonate or calcium silicate: which scale is on your tile
Both deposits are calcium and both show up at the waterline, but they form differently, look different, and come off differently. Telling them apart is the first thing we do, because the wrong method on the wrong scale either does nothing or damages the tile.
| Calcium carbonate | Calcium silicate | |
|---|---|---|
| Appearance | Bright white, chalky or flaky, often in a soft band that follows the waterline | Grey-white, glassy or waxy, harder and thinner, sometimes with a slight sheen |
| How it forms | Quickly, from high pH and high calcium hardness as water evaporates | Slowly, over a long period of high pH, often where water has been migrating through grout or plaster behind the tile |
| Acid test | Fizzes on contact with a drop of muriatic acid | Little or no reaction to acid |
| Removal | Responds to pumice on ceramic tile, scale-specific cleaners, or bead cleaning for heavy build-up | Needs bead cleaning; pumice and chemical cleaners make little impression |
| What it tells us | The pool chemistry has been running high for a while | Years of high chemistry, and possibly water moving behind the tile, which is worth a licensed pool contractor's look |
Most of what we see here is carbonate, because the fill water is hard and salt pools push pH up. Silicate turns up on older pools with several owners and no consistent chemistry. We test with a drop of acid on an inconspicuous spot, tell you which you have, and quote the method that fits.