Don't have trouble in my touch free but the friction units sling dirty water all over the walls, then the wax makes it kinda grimy. I tell the attendant if he can swipe a finger and see where he swiped, clean with dish detergent first., You can also use IBA presoak. We wash our busy machine and the walls at least once a week usually with Dawn platinum in warm water. If it's busy we will do it between cars and not even bother to rinse, the machine will do the rinsing as the cars are washing. Takes 30 minutes or less to touch up the machine and bay. The touch frees machines don't need that, and only gets acid washed every 1-3 months depending on volume.