Without unloader valves, your pressure washer would explode. Okay. Maybe not explode. But the results would not be pretty or functional. When you’re not using your pressure washer, and the machine is still on, pressure can continue to build. An unloader valve releases the pressure built up while the unit is inactive.
Some unloader valves are flow-actuated. This means that when the machine is in use and pumping water through itself, the valve will not be activated, since the flow continues. When the flow is shut off, however, the unloader valve opens to relieve the built up pressure.
Pressure-Actuated Unloader Valves
Pressure-actuated unloader valves are activated when the pressure inside the machine grows too high. At that point, the unloader valve opens, relieving the pump of the pressure it has built up.