The tile grout should be scraped out with a Grout Getter about 1/8” to 3/16’ below the top edge of the tile. This will allow enough room for the new grout to substantially fill in the grout joints.

The old remaining grout in the joints will act as a good roughed-up bonding surface for the new grout to adhere to.

Be sure to thoroughly clean out or vacuum the loose particles out of the grout joints before installation of the new tile grout.

The pictures show removal of sanded tile grout with the triangular cutting blade and the diamond cutting blade is removing non-sanded grout out of a 1/16” tile joint.