What is the best product to use to remove water calcium stains ?

Fill a spray bottle with a 50/50 solution of Dawn dish soap and vinegar. Spray it on the hard water stains and let it work. If they are tougher stains, you may have to scrub with a plastic scrubbie!

Have you tried CLR?

Where are the stains? Vinegar is great for this but you have to be careful and not damage your finish. If it's around faucets, you can place vinegar soaked paper towels and let soak. Then rinse clean.

Pumice stick- I found mine in cleaning section at Wal-Mart! It doesn't scratch any surface that I have used it on. I used to clean apts and this was a miracle worker for yucky toilets with stains from hard water and tenants not knowing how to scrub!! 😊

You might want to use a pumice stone. thats the only thing that cleans my toilets from well water and hard stains around my sinks etc.