How to fix discolored grout

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In the process of a home remodel, I've noticed the grout in my new bathroom varies in color. The tile installer and I agreed on a gray tone, which I see on the floor and maybe a wall or two. But the grout in the shower and other walls is definitely black. Can this be corrected without damaging the porcelain tile?

There's a good chance the grout for your project wasn't properly mixed. Fortunately, the problem can be fixed with no damage to your tile.

Essentially, your choices are to remove the grout or stain it. This can be a do-it-yourself project, though in your case you probably want the contractor to handle it.

Staining unsealed grout

Because sealant is intended to help grout resist moisture, staining will only work on unsealed grout. You can easily find grout stains in home improvement or tile stores.

Before you start staining grout, do these two things:

n Stain a small, inconspicuous area to be sure there's no damage and the color is correct.

n Thoroughly clean existing grout with a grout and tile cleaner and grout brush. This helps make the grout porous so stain evenly adheres. Let grout dry before applying stain. Also, remove any stain that comes in contact with tiles. While porcelain won't absorb the way other tile types might, you don't want stain to sit on the tile any longer than two hours.

Keep in mind that while it's possible to lighten a dark grout, the process may require multiple coats of stain.

Replacing original grout

You'll need grout remover and a manual or power grout removal tool, also available at home improvement or tile stores. Although porcelain tiles are quite durable, be careful not to nick or chip tiles during the removal process. Once the old grout is gone, simply install new grout. Follow package instructions and if the color is right this time, plan to apply grout sealer.

If grout work is something you'd rather pay someone to do, consider hiring a handyman service or an experienced tile installer. Top-rated grout companies say the cost to restain grout in a 6-by-10-foot tiled area ranges from $50 to $175; to re-grout the same size area is $240 to $350.

Be sure to hire pros with positive consumer reviews on a trusted online site and confirm they are appropriately licensed, insured and bonded.

Meanwhile, if you want grout to look good over time, avoid cleaning products with bleach or harsh chemicals. These can gradually erode grout, reducing repellency and leading to mildew and discoloration. If that happens, the only real fix is re-grouting. Consider periodically cleaning tiled surfaces with a solution of half-ammonia and half-water. For protection, wear rubber gloves and run the exhaust fan and/or open a window.