Natural DIY Cleaning Solution for Hard Water Stains.
To clean hard-water stains and scale from the sink, sprinkle baking soda over the sink then wipe down with a vinegar-soaked sponge. For tough stains use an eraser-style scrubber sponge.
Hardwater stains in a porcelain sink or tub can be scrubbed with cream of tartar sprinkle on a damp sponge. For really tough stains, try applying 3 percent hydrogen peroxide to the scale. Let soak a few minutes before wiping away.
To clean the drain ring, put a dab of toothpaste on an old toothbrush and brush in a circular motion, paying special attention to the groove around the ring.
For stubborn hard-water scale, soak a cloth in vinegar and let it sit on the stain for an hour or more. Wipe with the cloth when finished. Lemon juice can be used in the same fashion as vinegar to combat drain scale.