It is very easy to damage a variety of surfaces with a pressure washer, even the DIY brands with lower PSI/BAR ratings. The likes of limestone, mortar, decking, concrete and various other surfaces can be “etched” when too much pressure is used on them or the incorrect nozzles are used. “Etching” will be visible from lines being left in the surfaces which unfortunately once there cannot be reversed as it is permanent physical damage. We use professional grade petrol powered pressure washers which have built in unloader valves, this valve allows us to accurately adjust the levels of pressure we are putting out so we can adjust accordingly to suit the surface we are cleaning. We also use a variety of nozzle tips for our lances once again to cater to each surface.