You can clean tile grout without scrubbing, but the products you'd need to use contain some pretty harsh chemicals. If a simple and non-toxic method were available, it would be the best thing since sliced bread. In reality, a combined regime is needed to keep your grout ship shape.
Water, food and temperature
Since grout is a porous and rough surface, it tends to pose cleaning challenges that are not present on the surface of glazed tile or polished stone. Dirty-looking grout is usually a combination of dirt, mold and mildew. To be effectively cleaned, a combined attack is needed – one that reaches into the tiny pores of the grout and stops mildew at its source.
For molds and mildews to grow, they need a moisture source, a food source and a bit of warmth. Reducing the temperature of your shower to the temperature of a refrigerator is…well let's just say that’s not going to work. The best control is by reducing the food and water sources for mold. The food source for most of these molds is our own skin cells and the soaps we use. The Phosphates found in many soaps are also a great fertilizer for this growth. Keeping these residues at minimum levels will reduce potential mold growth.
To reduce moisture, you could squeegee or towel down the walls of your shower after every use. I’m not quite that motivated; in my home I leave the bath door wide open after a shower to allow the humidity to dissipate and this seems to work for me. Running a bathroom exhaust fan also helps pull humidity out of the room.
Why you need to scrub
Bleach is one of the most common substances used to “whiten” things, so you might be tempted to use it to whiten stained tile grout. While chlorine bleach does a great job of killing mold spores, simply spraying it on is not enough to break the mold growth triangle (water, food and temperature).
Here's why bleach alone won't work: The "dirt" in your tile grout is behind a layer of soap scum, and this layer need not be thick and obvious. Keep in mind most of these cleaning reactions are taking place at a molecular level and a layer of soap residue a thousandth of an inch thick can prevent the “bleach to dirt” contact.
That's why physical scrubbing or the use of acidic chemicals (like the phosphoric acid found in toilet bowl cleaner) can break trough this soap layer. One of the problems of using these harsh chemicals (aside from the environmental and skin contact issues) is the destructive effects to the grout itself. Grouts are cement based and can be eroded by acidic compounds. Bleach is less destructive to the grout than Phosphoric acid, but you'll need to scrub in order to for it to be effective.
Greener options than bleach for grout cleaning
One option is to regrout your tiles with a dark-colored grout. White grout is infinitely harder to keep looking nice than, say, a dark brown color. When I chose the grout for my own bath remodel, I used a non-sanded type in a “butter cream” shade for the shower, which complemented the tiles and was good match for the “sandstone” color grout I used in the travertine floor. These colors are pretty true to “dirt” in their appearance, so they look cleaner than white grout looks after several years of use.
If regrouting isn't for you, here are a few alternatives to bleach and corrosive chemicals:
- Networx editor Chaya Goodman Kurtz sprays hydrogen peroxide on her bathroom tile grout. She detailed the process on Hometalk.com, a social network all about home improvement. In short, you spray hydrogen peroxide on the surface, wait at least 30 minutes and then scrub with a nylon-bristle cleaning brush. As a whitening agent, hydrogen peroxide is remarkably effective, but has less-intense fumes than bleach.
- Vinegar (a dilute acid).
- Baking soda (here a poultice is made for scrubbing).
- A combination of baking soda and vinegar (chemical scrubbing happens automatically).
- Bon Ami (this is Calcium carbonate – a green option that will require some scrubbing).
- Borax (scrubbing required).
- Oxygen bleach powder.
- Steam cleaners (these use heat to your advantage).
Remember, ventilating your bathroom well to keep the humidity levels down is the best prevention.