The Whirl A Way is a good surface cleaner. If you are using a 4.5 gpm unit, you can easily run a 20" surface cleaner. I stock the 20" unit with removable wheels and offer it at an excellent price. Our #1 seller for mobile washers and the one I use, is the 28" Big Guy. I would not consider a unit with 3 spray bars, as you don't have enough gpm! Feel free to give me a call and I will be glad to answer any questions. We can get any surface cleaner that you want.