How to Clean Grout Without Ruining It

Step by step

1. 1

   Sweep and wet the grout

   Sweep or vacuum the floor so you are not scrubbing grit around. Then wipe the grout lines with warm water so they are damp before the cleaner goes on.

2. 2

   Mix the oxygen bleach

   Put on your gloves. Fill a bucket with 1 gallon of the warmest tap water you have. The label says to use the warmest water possible but never to heat or boil it.

   Fill the OxiClean scoop to line 3 and stir until it dissolves completely. That is what the tub label says; OxiClean’s website lists line 4, so go by the label on your own tub.

   What it looks like: water with no gritty powder left on the bottom of the bucket.

3. 3

   Spread it on and let it stand

   Pour or sponge the solution onto one small section of grout, and let it stand 5 to 30 minutes, which is the label’s time for hard surfaces. OxiClean says to work in small areas so the solution does not dry on the surface, so add a splash more if it starts to dry.

4. 4

   Scrub with a nylon brush

   Scrub each line with a nylon grout brush in short back-and-forth strokes. Custom Building Products, a grout maker, recommends a white nylon pad with its own tile cleaner to avoid scratching tile, so stay with nylon.

1. 5

   Rinse and blot dry

   Rinse the section with clean water and blot it dry with an old towel, which is how OxiClean’s directions finish. Then move to the next section and repeat Steps 3 to 5.

2. 6

   Let it dry, then check it

   Wait until the floor is fully dry before you judge it. If some lines are still dark, repeat Steps 3 to 5 on just those lines.

3. 7

   Seal it (cement grout only)

   Sealing is optional, but it helps clean grout resist stains. These directions come from the TileLab Grout & Tile Sealer data sheet, so follow the label on whatever sealer you buy.

   1. Start with grout that is clean and completely dry. New grout needs at least 48 hours after it was put in.
   2. Wear chemical-resistant gloves, such as nitrile.
   3. Brush or sponge the sealer onto the grout and let it soak in for up to 5 minutes.
   4. Wipe off any extra right away.
   5. If the first coat soaked right in, put on a second coat the same way.
   6. After 2 hours, drip a few drops of water on the grout. If the water soaks in right away, add another coat.

   What it looks like when it is sealed: the water drops sit on top of the grout instead of soaking straight in.

Keep it clean between scrubs

For everyday cleaning, use a pH-neutral cleaner, meaning one that is neither acid nor strongly alkaline. Scott Carothers, writing for the tile trade magazine Stone World, recommends a pH-neutral cleaner for routine cleaning of cement grout.

When it will not work, and what to do instead

Grout does not always come clean on the first pass. Here is what to do then.

• You heard vinegar is the cheap way to clean grout. It is easy to see why, since vinegar cleans so many things. But Custom Building Products warns that acids may etch, lighten or change the color of cement grout, and Stone World says acid leaves grout more porous, so it gathers dirt faster.
• The lines are still dark after two rounds. If the grout is cracked or crumbling, a tile pro can tell you whether it needs regrouting.
• Dark spots in the shower come right back. The EPA says more ventilation and more frequent cleaning usually stop shower mold from coming back. If the mold covers more than about 10 square feet, the EPA points you to its professional cleanup guidance. The habits are in Why shower mold keeps coming back.

Why it works

Cement grout is strongly alkaline, the opposite of an acid. Stone World puts Portland cement grout at a pH of about 11 to 13, way up at the alkaline end of the scale.

That is why acid is the wrong tool. Stone World says acid makes the grout more porous. Think of a kitchen sponge: one with bigger holes soaks up more of whatever spills on it, and grout with bigger pores soaks up more dirt.

Oxygen bleach powder is a cleaner whose label lists grout as a use, so you get the dirt out without reaching for an acid. A penetrating sealer then soaks in and helps the grout resist most common stains, according to the maker’s data sheet.