I am thinking of replacing existing tile on my bathroom floor. So I would like to know if new tile can be placed over the existing tile? If so could the new tile be placed over the existing tile if it is not on a concrete floor?

Existing tiles should be removed before installing new tiles on the floor. It is possible to install new tiles over the old ones when the sub-floor is concrete, but this will change the height of the floor itself, which may affect the current or future installation of materials. 

To remove existing tiles, use a chisel and hammer to loosen the grout around the tiles until the tile itself can be lifted up and out of the floor. Use a power grinder to remove any adhesive and even out the sub-floor surface before moving forward with the new tile installation.

Old tiles can be reused elsewhere in your home or donated to a building salvage yard, so take care to remove as many whole tiles as possible when chiseling them out of the floor. Even if you no longer like the tiles for your bathroom, they could work well in a mudroom, laundry room, or someone else’s home.