Ok inwill wait on the acid. Will they and use brushes and gm. Does it help to add more groutmaster?? Or it that just wasting it?bro
i have been cleaning tile and grout for 15 years....
i used acid for the first 3-5 years....frequently had some issue with it....
even 1 problem is enough to get rid of the stuff......
with a CRB or a good scrubbing with grout brush and GM....
i clean grout better , safer, less risk, cleaner, and quicker than i ever did using acid......