Not sure if this is up our alley

Hi guys…

Not sure if this is something I could help the customer with… But I thought I’d put it out there if anyone knew or has an idea on what these stains are / ideas on how to get rid of these…

The first picture looks like the grout has spread somehow… These tiles are in an indoor swimming pool at an aged care…

The second /3rd picture is in the change rooms of the swimming pool… (I hope they upload in the right order)…

They really are not sure how they’ve appeared. Even if it’s not up my alley to clean up, if I give them some sort of advice, it could open up a door to pressure wash their exterior pathways etc at this aged care…

If anyone has an idea how these have come by or on how to get rid of this, any advice would be appreciated…



Hydrochloric acid may get rid of the staining. On those other two photos the tiles look like the glaze is gone on the high spots. Tell those old folks to quit shuffling their feet