Help with kitchen floor tile grout
We had a flood in our recently remodeled (1 year ago) kitchen, water stood for a few days while we were away. As a result some of the grout (probably quarter of the kitchen floor) is covered with some sort of white powder/residue which doesn't come out with regular floor washing. We have big 16x24 brown-gold italian ceramic tiles with gray/brown grout. One contractor said he will use some sort of wash to remove the it, another suggested to scrape discolored grout out and re-grout. What is the right way?