pressure washing help

[thomas.mccalpin]

Hey guys, i have a block retaining wall out my my pool and it is starting to look pretty dingy. What chemical can i use along with my pressure washer to get the best results? I have a 7hp 3500 psi troy bilt with the various heads for the wand.:usflag: Thanks

[Happy Frog]

What do you call looking dingy? :confused:
If you want a chemical recommendation, you need to give more information :hammerhead:

[thomas.mccalpin]

it is grey decorative concrete blocks that you see everywhere. They are turning black on the face of the stone. Looks like dirt but it is not. any help will be greatly appreciated.*trucewhiteflag*

[Happy Frog]

Sounds like mold...
Chlorine and Simple Cherry will take care of it in no time...