Grout touch up

I've often been asked if the old grout needs to be removed in order to fill in some voids that need to be filled in.
If you have a crack or void in your floor (or wall) grout that may have occurred by expansion joints or merely because the installer in grouting overlooked a void, they can and ought to be filled. Sometimes in the grouting process only the thinness of grout may fill the joint and everything appears normal at the time of the original installation. In time that shallow grout might develop into a void.
If you have spare grout, you need only remove any grout that is loose (with your finger or vacuum), mix a little of the powdered new dry grout with water into a paste in a little dixie cup or something, and fill the void with your finger. Especially if there is but a hole or two.
Let the grout set for a few minutes and gently wipe the repaired hole with a wrung out wet sponge, or even a paper towel - wet or dry. A small hole can be repaired in minutes and wiped clean in seconds with a paper towel.