Take a look at my Hubpage. I go into detail of how I finally found something that worked. I've been obsessed with getting rid of Hard Water Spots and Stains for years off my Mother's headstone. I'm telling you, all that stuff on the shelf at the hardware store and the supermarket sucks. It's all either acid based or it has abrasive pumice mixed into it.
Depending on your water situation, does it have softeners in it or is full of minerals like well water has? If you get tons of residue on your walls and floor when the water dries, then you have heavy alkalinity in your water. Mineral deposits is the result.
Mineral deposits and limescale is something you'll just have to continue to treat. I found this stuff at http://www.AmazDepot.com that sells a Water Stain Remover that works great. No harsh chemicals or abrasives to scratch. It good stuff. I used it on my Mother's headstone and it worked like a charm.
You could use EDTA to break apart the hard water deposit bonds, then scrub off. But EDTA is expensive. Lemon juice and vinegar suck too. They DO NOT work!!!!!
Limeaway is nothing but diluted Phosphoric Acid. It's over priced junk. You can buy Heavy concentrates of phosphoric acid from chemical supply companies on the internet. Heavy concentrates of the acid work great on glass and showers, but the fumes are super toxic and will eat away at your skin if you don't wear gloves.
Anyway, go to my Hub to see how my Headstone project turned out. It's pretty impressive!!!