Acid-based cleaners will eat your grout

Q: My mid-'80s home has two bathrooms with shower tile installed directly on waterproof (I hope) drywall. One is a tub enclosure, one a shower-pan installation. About three years ago, I used a commercial cleaning product on both enclosures that claimed to be specifically intended for tile and grout. While using it, I noticed a lot of gritty material washing down the drain with the rinse water. I now believe that this product destroyed the watertight surface of the cured grout.

Since then, both enclosures have developed moisture seepage through the grout (and the ceilings below). When the first enclosure showed problems, I tried using a commercially available sealer (masonry-type intended for grout) on both enclosures, but this had little effect.

I ended up pulling the tile and the drywall beneath, thinking that the problem was a plumbing leak. Some $2,000 in repair work later, the only suspicious-looking area in the tear-off was about 4-6 square feet of wall behind the tile surrounding the soap dish, where it was intact but mildewed.

Now the second enclosure is seeping through the grout and causing a similar problem. I tried yet another commercial sealer; again, not successful. The grout appears to be completely intact except for this wicking problem. I called a local business that advertises a sealing process, but it sounds like they apply essentially the same product and do not warranty it more than a year.

Is there some type of stronger product/process for resolving this problem? I am not eager to tear out another tile job.

A: Grout is a cement-based product, and therefore by default is alkaline. Reading how you made your grout runny, it is apparent you used an acidic cleaner.

Yes, the cleaner may have been advertised as a tile-and-grout cleaner, but acid-based materials are the mortal enemy of grout, stone, marble and granite. Acid doesn't actually clean, it strips and etches. Acid eats up minerals, calcium, efflorescence, porcelain and rusts. Acid is used to clean up cement residue in construction. That pitted porcelain sink or toilet bowl in your bathroom has also been exposed to acidic bathroom or toilet cleaners.

Not believing that an acidic material advertised as a grout cleaner was being peddled to the public, I perused the aisle of my local big-box hardware store. Sure enough, on sale this week I found "grout cleaner" with listed acid ingredients, no listed pH and a warning about exposing the material to marble. While it will effectively clean (and remove) that grout with little or no scrubbing, it will also etch vulnerable materials it comes into contact with.

If you are unsure if your cleaner has acidic properties, dump baking soda into a sample. If it fizzes, you have an acid product and should not use it anywhere near your grout.

Use an alkaline or neutral cleaner next time. They are widely available. An alkaline cleaner will actually help restore the grout by improving it chemically.

The pH scale goes from 1 (acidic) to 14 (alkaline). Pure water is absolutely neutral at 7, battery acid is about 1; vinegar, orange juice, tomatoes, and soda are all between 2 and 4, while soapy water comes in at 12. Using this knowledge, we can see why grout on kitchen counters is so commonly deteriorated where some foods are prepared and spilled.

On the other side of the spectrum, contrary to popular belief, taking a squeegee to the tile walls of the shower may otherwise be causing harm by removing the protective soap scum. Structurally, some of the best tile showers are also the grossest. Jeff Whittington, owner of About Grout, backs me up on this, and adds that the soap also helps to seal the grout.

Yes, as you suspected, the acid removed the patina from your grout, thereby making it lose what little resistance to water it had to begin with. Patina is the glossy, film-like surface that covers paints and grout. Also note that you do not have "waterproof" drywall behind your shower walls. There is no such beast. Water-resistant "greenboard" is used here; it has a more durable paper coating than standard drywall, dissolving in 10 minutes, rather than five, when exposed to water.

Whittington wanted me to personally thank the builders and tile setters in homes built from your era up through 1992 for indirectly putting his kids through college. How come? Find out why in next week's column on substrates, grout types and grout sealing.

Darrell Hay answers readers' questions. Call 206-464-8514 to record your question. Or e-mail dhay@seattletimes.com. Sorry, no personal replies.