How to Bleach Grout
- 1). Dissolve a powdered oxygen bleach in water, according to the manufacturer’s instructions.
- 2). Pour the bleach solution onto the floor or countertop. Make sure the solution floods the grout lines. Allow the bleach to soak into the grout for at least 15 minutes. Oxygen ions in the bleach work to loosen and remove the stains that discolor grout.
- 3). Scrub the grout with a scrub brush. If the grout is not severely stained, this may be enough to get it clean. If not, pour on more bleach solution, and repeat the process as necessary.
Source...