Lots of minerals in water that will turn everything white. It is one of the hazards of black grout. I assumed you used a good sealer?

This is in a hallway and powder room, so minimal exposure to water. The grout that was used supposedly has a built in sealer, but I wonder if I need to apply additional sealant. It is a matte porcelain tile.

The 'frequent' wetting with the scrubbing you are doing might be a vicious cycle of efflorescence... salt in the water coming up to the surface later after it dries. I would definitely seal it when it is dry and black.

Got a picture? Assume it's the floor? What are you scrubbing with?

Unfortunately cannot get a photo to download. Cleaning with standard grout cleaner. Grout is TEC

You have to wait for the picture to lose its grayed effect and really clarify...before you hit the submit button .

If you tell me the flooring outside the powder room is wood? I'd have said run it right into the powder room : ) No grout.

You have to upload a jpg. If not a jpg, won't upload.