Drain and clean with Lime Away. Might have to apply several costings or keep soaking it until it's clean.
CLR is *Amazing!! For Calcium & Lime build up. We've been dealing with it majorly (esp this last year) all of the sudden. Recomend getting a scrub brush w/ a plastic scraper @ the end typically in cleaning isle ... if you're dealing w/ thicker areas. CLR is a truly good product.
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