The answer to 'why is my pressure washer moldy' is that mold can build up in the pressure washer's water supply lines, pump, and other internal components if the equipment is not properly stored and maintained. Mold thrives in damp, dark environments and can quickly grow inside a pressure washer that has been left with water sitting in it.
Some common symptoms of a moldy pressure washer include a musty odor, visible mold growth, and reduced pressure or performance. To prevent and address mold issues, it's important to properly clean and store the pressure washer after each use, drain all water from the system, and keep the equipment in a dry, well-ventilated area.