White staining on tile grout - water leakage?

[Mike Shumack]

I have this white staining on the tile grout in the bath. To me that means I'm getting water from somewhere.
Looking in the opening behind/under the toilet, I don't see any obvious signs of leakage - and the white stain doesn't seem to go all the way to the toilet. I also don't see any signs of leakage at the wall (wallpaper and wood trim look good).

I suppose this could mean the plywood under the tile is wet. I'm not sure.

What do you think is going on? has anyone else had this in their coach?

[Fred Brooks]

    Hi Mike, Did you buy the coach new? Looks like a previous repair from the pattern of the grout that may have replaced. Usually grout turns darker when wet and then lightens up after cure. Real mystery! Merry Christmas, Fred

[Mike Shumack]

The Coach is a 2005. I bought it in 2018. I'm the third owner.
However, that white staining was not there when I bought the Coach. Maybe some water spilled/sat on the tile and that is efflorescence I'm seeing.
I can scrape it off (it doesn't go all the way through grout).

I had to reattach a few tiles in front of the shower. I have not grouted those yet, so I think I will use the Epoxy gout (SpectraLock) and re-grout the toilet area when I do the shower area.
At least with SpectraLock grout it won't stain.  SpectraLock

As long as there is nothing going on under the tile (like wet plywood) I should be okay. I don't think the plywood is wet as this white stain is on top of grout and not coming up from the bottom side.

[Joel Ashley]

In my granted limited experience with floor tile, if water gets under them the mastic/mortar lets go and the tile feels loose.  If they aren’t loose I’d think your underlayment is okay.  The white removable “stain” may just be some other surface spill deposit.

Since you have reattachment experience, and want to regrout anyway, you could try pulling one of the toilet tiles to check underneath.  If it doesn’t want to come up easily, I reckon I wouldn’t risk cracking it, and just regrout.

Joel