How do I remove calcium deposits from pool tile?

Use muriatic acid (with caution). It dissolves calcium carbonate scale that scrubbing alone can’t remove. Wear gloves, goggles, and old clothes. Dilute it 1:10 (acid to water — always add acid to water, not the reverse). Apply with a brush or sprayer, let sit briefly, then scrub and rinse thoroughly. Don’t let it dry on tile, and avoid metal or stone coping. For fiberglass pools or gentler options, use a pumice stone or specialty calcium remover. Test a small area first.