We have recently had installed new tile shower flooring. We have noticed a small water leak in the wall floor behind the shower (in our closet). The leak is not constant and only happens every few times that we shower. The person that installed the flooring says that he installed a cement concaved floor under the tile so that there is no way the floor is leaking. We are thinking that there may be something going on with the diverter or the in the piping itself due to it is not a constant leak. Any advice would be appreciated.

It could be water getting into the wall around the escutcheon around the faucet. Another place could be around a soap dish or a towel bar. Look every where before you tear up the floor

Is the shower valve in the wall between the shower and the closet?

Did the guy put a membrane under the cement floor of the shower and take it up the walls before he poured the floor for the tile? If not then you've got problems. Check for small cracks on the tie joints, in the corners of the shower, at the base. If there are cracks then that's propably where the water is coming from. Good luck-----Zeke----