QUESTION

Cleaning Ceramic Tile Wet Stains - We have put a bid on a house and when we went to do the inspection, someone had left the faucet running in the kitchen sink and put the stopper in. The kitchen was flooded and probably had water flooding for at least 12 hours. Kitchen flooring is ceramic (glazed) tile and all of the tiles have gray colored stain marks running the entire length of the kitchen and dining room right along the "water line" of where the water was running from the sink. Each of the stains are from the outside of the tiles going inward. We thought at first it was moisture from underneath the tile but after a period of 3 days, the stains are still the same so it's not due to moisture. We've tried vinegar, bleach, various tile cleaners, grout haze remover, but nothing is removing these stains. Any ideas on what we could try to remove these stains? I've been told to try straight muratic acid (been assured it won't ruin the tile) but wanted to run this by you first to see if you had ever heard of this or have any other possible solutions.

ANSWER

ANSWER - Whatever you do, do not use any acid, and in particular do not use muriatic acid, which is very corrosive and could etch and damage the tile.

If the gray stains were not there before the flood instance, the stains are in the area where it was subjected to the floor water, and the stains are emanating from the grout joint towards the center of the tile, then they are likely damp stains.  Three days may not be nearly long enough for the tile to dry out considering it has an impervious glazed surface and can only dry through the grout joints.

I have seen this occur with lighter colored glazed ceramic tiles that have a porous clay body.  The water goes through the porous cementitious grout and the porous clay tile body absorbs the moisture.  Then it may take weeks to dry out completely depending on the temperature and humidity of the room and the extent of moisture content in the concrete substrate that I assume it is attached to.  Water that reached the tile through the grout joint likely got absorbed into the concrete substrate, so the drying process requires the concrete slab to dry too so moisture doesn't continue to migrate up to the tile keeping it damp longer.  You can use heat lamps and fans to try to speed up the drying process.

If the substrate is not a concrete slab, but is over a wood subfloor then there could be other concerns too.

Good Luck.