How to Fix Grout in a Shower

Remove the damaged grout from between the shower tiles with a grout saw by pushing the saw forward and back over the grout, digging into it. Remove all cracked or crumbling grout from each line and an inch or two of the good grout at either end.

Thoroughly clean the tiles (and the exposed grout lines) with tile cleanser and a scrub brush. Rinse very well. Proceed with the project while the tiles and lines are still wet.

Add grout mix and water together in a bucket in the ratio specified on the grout packaging (it will vary by brand). Use enough to cover all the exposed grout lines.

Mix the grout and water with your drill and mixing bar. Mix it well. Let it sit in the bucket for 10 minutes. Mix it again.

Apply the grout to the open joints on the shower walls using a grout float, starting at the highest part of the lines and working your way down. For each line, wipe the grout over the surface, then scrape the long edge of the float over the line at a diagonal angle to force it down into it. Do this to all the lines.

Let the grout sit in the lines for 10 minutes. Wipe off the excess grout using a damp sponge. Let it set for 24 hours.

Apply a coat of grout sealant over the grout lines with your sponge applicator. Let it set for 12 hours. Apply a second coat in the same manner. Let it set for 24 hours before using the shower.