Leslie's Acid Free Scale and Stain Remover removes scale and calcium build-up.

Before applying Ultimate Rapid Scale Remover, scrub surface of calcium with scrubbing pad or scraper blade to break up first layer of scale.
Apply product liberally to scrubbed surfaces and let sit several minutes. Product will bubble initially, showing it is working.
Scrub the area again, breaking the next layer of scale. Calcium/scale will come off in layers just as it built up.
Apply product and repeat until area is completely clean of calcium buildup.
Rinse thoroughly when finished.
Covers approximately 50-100 sq ft/quart.

Leslie's - Ultimate Rapid Scale Remover 1 Qt