If you're looking for a tool to speed up the process of removing damaged or mildewed grout, then Grout Grabber is for you.
The Grout Grabber kit includes 1 adapter, 1 carbide grit blade, and 1 Allen wrench. You'll need a reciprocating saw, preferably cordless.
Using the Allen wrench, mount the grout grabber adapter and carbide grit blade on a reciprocating saw. To remove existing grout, approach the grout line at a low speed and cut into the joint until you reach the bottom of the joint.
It is especially comfortable to hold the saw in an upside-down position. At the bottom of the joint, increase saw speed and pull backwards—never use Grout Grabber at full speed.
Be especially careful as you approach a grout intersection. A tile or two may be out of alignment, and it is possible to chip a tile's edge with the tool. Pay attention—but let your tool do the work.
The replaceable carbide grit-coated blades are 1/16" thick, which allows you to work with tiles that have a thin grout line. On the other hand, you can add a total of 4 blades to the shaft (two on each side) to cut grout lines up to 1/2" in a single pass. Wider grout lines can be cut with a second pass. It is important to choose a blade thickness less than the joint width to prevent the tool from binding in the grout line and damaging the edges of the tiles.
Whether you are a homeowner or a professional, this tool will get about 300 square feet from a single blade depending on how old the grout is and the type of grout used. There is very little grout dust, but it will be very fine, so be sure to use a good shop vac or a vacuum that has a clean bag and filter to prevent blowing the dust back out into the room.