Tile and grout cleaning has many different factors that we look at to judge cleaning capabilities. One thing that we always look at is how the grout is holding up. What I mean by this is if the grout lines have become porous, or are now cracking and busting up our cleaning process has the potential to break it up even more. The other problem you will have is it is near impossible to have someone come in and replace just that section while having it match up perfectly to the other 20 year old worn tile and grout.
Another thing we look at is what color the grout originally was. We normally look in closets or places of low traffic, and soiling as it will be the cleanest and most original. The reasoning f0or this is many times people forget that the grout was originally gray not white. We can’t turn a grey grout white obviously so we just make sure to point all of that out to them.
A third thing we look for is multiple spots of color variation within the grout lines. If there’s a lot of this going on that tells me the tile installer missed spots when sealing. This can greatly effect our cleaning of the mis-colored areas as what happens when those spots are missed they become very porous and allow the soiling to get down deep within the piece. Sometimes no matter what we try those places will still be a shade different as our cleaner cant get down underneath the sealer as it isn’t meant to.