Teal Green Chalky deposits on Spa Grout

[menlospa]

I have teal, chalky deposits all over the tile grout of an older spa. I have drained it and tried brushing, but nothing short of a putty knife removes it. Is there a product out there that I could just spray on and rinse, kind-of like easy off for pools?

[gude2shoes]

I have the same problem on a brand new pool. The grout has turned from a grey to a white color. I have tried using coca-cola, ammonia, peroxide and a pool/tile scrubber with no success.
Help please![/i]

[bambino]

Try muriatic acid. First use it diluted 1:1 with water. If that doesn't work you can try it full strength.

The acid releases fumes so wear a mask and eye protection and never work alone!

You can apply the acid with a soft brush, rub it around and then rinse it off with fresh water immediately. If the acid stays on too long it softens the grout too much and eats it away.

NEVER use anything with metal for the acid wash. The muriatic acid will eat through the metal in no time.