Removing bathroom grout is a messy job, but the right tools can make it neater and less physically gruelling. You must break the grout into dust for removal because prying up chunks of grout can damage the surrounding tiles. Some tools are adequate for removing a small amount of grout, such as when you are replacing a few cracked tiles. But for larger jobs, such as repairing the damaged grout throughout your bathroom, power tools are more appropriate.
A grout saw is a hand tool with a thin carbide blade that allows you to manually saw your bathroom grout into dust. The grout saw's blade is sharp enough to damage the surrounding tile, so you must be careful not to touch the tiles. Because a grout saw requires manual effort, it is most appropriate for small jobs.
A utility knife's blade is thinner than a grout saw's blade, which makes it appropriate for removing grout when your bathroom's grout lines are very small. If your bathroom tiles are self-spacing, then you must use a utility knife instead of a grout saw to remove the grout.
A rotary cutter is a power tool that spins an attachment rapidly. A rotary cutter fitted with a grout bit can quickly reduce bathroom grout to dust. The rotary cutter's grout bit will not damage tiles if you graze them slightly, but can scratch or cut tiles with prolonged contact. Since the rotary cutter is a power tool, it is suited for large grout removal jobs, but it can also be used for removing small amounts of bathroom grout.
Chemical Grout Removers
Chemical grout removers are acid-based products that eat away your bathroom grout. Chemical grout removers aren't appropriate for all types of tiles, but they will not damage porcelain and glazed ceramic tiles, which are commonly used in bathrooms. Chemical grout removers eat away the top layer of grout, which creates a groove that will hold new grout. This makes them appropriate for regrouting the entire bathroom, but not for removing a damaged tile, since all of the surrounding grout must be removed in that case.
A wet-dry vacuum picks up the majority of the grout dust produced by grout saws, utility knives and rotary cutters. You can use the wet-dry vacuum after you have reduced all the grout to dust, or you can have a helper hold the vacuum's hose near the cutting tool to catch the clouds of dust before they can settle on the tiles.