Originally posted by @Steven Hershey:@Daniel Hughes Im not 100% but i will be employed with this company until i retire.let me just challenge this brotha by the other side of this right, so think of the INFINITE realities in which you do switch jobs, move, goals change, triplets, divorce, family death, acid to the eyes and you go blind, you see where i am going with this.

Chlorine contact time with organics does eventually produce Trihalomethanes and Haloacetic acids (TTHM & HAA5s).

Muradic acid left in over night and it would be clean 

I have had buildings where new AC systems are installed at the same time, and without exceptions, the pet occupied units will clog and need acid washing sooner, and will break down sooner.I no longer allow dogs but still allow cats.What are things your tenants' pet did that cost you time and money? 

That stuff will eat your hands right off your wrists Thats basically Sulfuric acid , if you do use it watch out for eruptions .Have a towel ready to cover the drain . 

For sanded grout, I had some VERY discolored light grey grout in a bathroom and the only thing that worked was phosphoric acid (a long time ago it was in tilex and the works) but now I think you have to order Lime-B-Gone from a restaurant supply (or amazon).I would ignore very small hairline cracks.

Any previous use of the property involve chemicals, acid or poisons?

If that doesn't work use muratic acid. 5 parts water to one part acid.

I love acid stained concrete, I enjoy the look of it, and the easy maintenance.

I could have an excellent carpenter that just don't clean up well, or a good stucco plasterer but leaves wet stucco on my brick pavers for me to clean up with muriatic acid...Give you another example.