How to remove water stains off tiles

Does anyone have a proven method of removing water stains off tiles? We have tried vinegar and a spot remover without luck. Any ideas?:thanks

Which spot remover? I use 30Seconds Spot stuff as we have hard water and it's brilliant.
Of course, is yours actually a hard water issue or something else?
Mould? Acidic (soft_ water? Soap scum?

That is what we have tried. The stains are fairly old so I will continue trying over the next week. I have used this on the bathroom successfully and then added the sealer. Thanks for your answer.:thanks

I got this off Google for you-----Use a 3% hydrogen peroxide to remove stains from ceramic and porcelain. For gentle surface cleaning you can make a paste with one part peroxide and two parts baking soda. Apply the paste and let it sit for about 30 minutes before scrubbing and rinsing. You can also pour peroxide directly on stubborn stains.

There are other ideas too!

We tried using 30 second spot remover again - applied it to the stain and left it for half an hour then scrubbed it off and that has worked. It seems that the answer is to leave it on for a while.

Thank you, Peroska and thank you Bryan. Much appreciated.:thanks

I've also had incredible results with 30 Second