[LazyPup]

When i was working maintenance for a city school system in Massachusetts I had to regrout an entire 35' x 100' girls locker room, floors and walls, including 24 shower stalls because the custodians had repeatedly used muriatic over the years and the grout was now porous allowing water to go through the floor and ceiiing below into the boys locker room.

On the lighter side,,,,,,,I just happened to be looking at the book for my ROTO-ZIP and discovered that they make a special bit for removing tile grout. Use the router base attachment to maintain the depth and work carefully that should make quick order of removng the excess.