Actually, regrouting bathroom tile is one of the dark secrets of home renovation: it's dead-simple. While there is the probability of damaging your existing tile, the probability is not very high. We'll show you how to avoid this.
In a Nutshell: How to Regrout Bathroom Tile
Remove existing grout and then add new grout to the open seams. That's the process.One thing you definitely do not want to do is try to grout over existing grout. After all, when you look at tile grout, it does form a channel--and can't you just fill in that channel with more grout?
No. Old bathroom tile grout is no longer porous. Its porosity has been compromised by years of soap scum and possibly tile sealant. The best course of action is to rip out the old grout and replace it.
- Remove Old Tile Grout: Your best friend is any type of Dremel-type rotozip or oscillating power tool. These tools, along with some hand work, will completely rid your tile of all grout.
- Apply New Tile Grout: Mix dry grout (or use pre-mixed grout), apply with a trowel, squeeze into the seams, and remove excess grout with a rubber float.

