1500 to 2000 PSI MAX. If you decide to use a pressure washer to clean your pergola or outdoor cover, that is far more efficient than garden hoses and use less water, we highly recommend using low pressure only. Our experts recommend choosing a pressure washer with a setting option of 1500 to 2000 PSI. It is the safe pressure suggested for cars, so you won’t need to worry about damaging or removing some of the powder coating from the aluminum. Azenco’s warranty does not cover powder coating damages caused by above 2000 PSI pressure cleaning.