Hi i have a GP 18inch hammerhead surface cleaner. It works ok. I love it on roofs, but on driveways it seems to leave straight lines where it has been. I will walk so slow its like i am not moving and it still dose it. Then on the next driveway it is fine and i can walk fast and no lines. I clean the nozzles before every use and no change. Also i had to put a ball valve on it because it slowly leaks water out of the nozzles. (without the handle being held in). This surface cleaner is only a few months old and i want to get one i wont have these problems with. Could the lines be a water flow issue i was running 4000 psi unit at 4gpm. I just picked up another unit and will now be using 4000psi at 8gpm. I want a surface cleaner at least 22inch. What do you guys think is the best one out there?