Water enters the pressure washer via a garden hose (a) and moves through a pump, which consists of a series of two or three plungers (b) arranged in a line or a circle. The plungers are powered by an output shaft on the engine or from a motor. Each plunger boosts the water pressure sequentially, one feeding higher pressure water to the plunger next in line.
The last pulse of high-pressure water exits the pump. The water then moves through a component called the unloader (c). This component unloads water if it gets too hot because the gun’s trigger is off. Next, the water travels down the hose to the gun (d). When you pull the gun’s trigger, you send a series of high-pressure pulses of water out the nozzle.
“It’s important to understand that the pump produces cleaning and rinsing efficiencies with high-velocity water pulsations,” says Vince Morabit, a mechanical engineer who’s designed and developed outdoor power equipment from pumps to chainsaws since the early 1960s. “Think of it this way: The kinetic energy in that pulse of water is like a chisel being struck repeatedly by a hammer.”
And since residential pressure washers also dispense cleaner, either out of a built-in tank (e) or by siphoning it out of a bucket, they clean via mechanical and chemical means. You apply the cleaner and then rinse the surface. The cycle is always the same: clean, rinse, repeat.
“The cleaning agent you use is as important as the pressure washer itself,” says Morabit. By selecting the right one, you rely less on the pressure washer’s force and more on the gentle removal of grime by the chemical action of the cleaner.
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