There is this crappy carpet at a carpet store that I clean .. Im having a tough time with a path from the warehouse to the front of the store .. it wont stay clean .. in fact I did it last night and they called today at 4pm and said its getting darker ..the warehouse has concrete floor .. they drive forklifts around .. they say they mop the concrete 3 times a day .. my water coming in at the wand had a PH of 4-5 and the pre-spray in my hydroforce was a PH of 8-9 before diluting with water as I spray the carpet .. anyone out there have any ideas ..?? thanks!! Paul