To prevent damage when power washing concrete and other surfaces, start gently and build up only if you need to. Begin with low pressure using a wide fan nozzle.Choosing Nozzles and Lances for Power Washing Safely, ideally around 1,000 to 1,500 PSI with a 25° to 40° tip usePSI and Flow Rates for Power Washing, then do a small test spot in a hidden area for about 30...