Help- hard water stains on slate tile
We began renting a home a few months ago. In the master bathroom there is beautiful slate tiling on the floor and in the shower. It is the rough, natural stone. I have no idea how it was sealed. Since we moved, in the tiles in the shower have looked worse and worse as the hard water stains have increased. We do not have a water softener, and the owner is not interested in installing one. I called the previous renter to ask what she did to clean it. She said she just used regular cleaner. I was skeptical whether I should use that on slate, but tried anyway, and it didn't seem to help. What can I do? I don't care to spend a great deal of money on it as it is not our home, but I would like to keep it looking nice. If anyone has any suggestions, I would really appreciate it. Thank you!