If your travertine tile is polished and water stains are dull marks then it will be surface damage
created by acidic substances. To remove such a type of stains you should buy good quality marble repair kit. If your tile is hone finished and the water stain is darker then you have to use one sealant to prevent further staining.
It is very easy to clean these type of stones. First we take a old brush and warm water. Then clean the tiles. Next we use the vinegar and apply the stones. Vinegar helps to clean the tiles and clean the small corners with a tooth brush.