We will ask you what kind of stains are on your concrete so we can address the problem.
Some detergents are for eliminating mold - some are to clean off clay - others are for leaf impressions - we can also lighten rust stains - disperse oil and remove chewing gum.
AtlantaBlue Pressurewash Company has hot water machines -
Here is an example of washing a vertical wall: http://youtu.be/5F2vSL89UuE
AtlantaBlue Pressurewash has an 8pgm machine and a 5.5 gpm machine both with water tanks.