Recently a customer purchased a pressure washer from us. Within days they called complaining that the pressure washer did not work properly; they were not getting pressure. The implication was that this was a warranty issue. We asked them to bring the pressure washer in so we could look at it.
The mechanic checked the inlet filter and found it clogged with dirt and debris. The pressure washer was not getting adequate water flow, causing it to surge, and lose pressure. As soon as the mechanic cleaned out the filter it worked perfectly. Fortunately, the situation was resolved quickly as lack of water flow causes cavitation that can damage water seals o-rings and worse.
The moral of story is always inspect your inlet water filters before you start using your pressure washer.
Here is a picture of the bag of dirt that we pulled out of the inlet filter.