Pressure Washer Unloader Valve Guide

Getting a phone call while pressure washing a truck or needing to set the nozzle down to attend to a pet are common occurrences. However, releasing the nozzle and leaving the pump running could end up being very costly. 

As a pump runs, it builds pressure, but with the nozzle off, there is no relief. Without a way to relieve that pressure, the pump will eventually burn out, leaving the user with a malfunctioning unit. Because distractions are inevitable, a quality unloader valve is necessary to protect the investment and prevent the pump from burning out. 

The Importance of an Unloader Valve? 

In a pressure washer, water is pumped in faster than it is let out. This creates the high-pressure water used to blast surfaces clean. 

However, if the pressure washer gun is disengaged and there is no unloader valve to redirect the pressurized water, the pressure will continue to build. It would not take long for the pressure to exceed the components' PSI limitations and damage the pump, gun, or hoses. Water being pressurized by the pump must be redirected once the spray nozzle closes, which is the primary function of the unloader valve. 

How an Unloader Valve Works 

As the trigger on a spray gun is released, pressure builds, and water backs up into the head of the unloader valve. This causes the spring tension to be overridden, which allows the water to flow past the valve ball and out through the bypass port. 

Once the trigger is squeezed again, the spring tension returns, the valve ball resets, and the water flows out through the gun. 

When the unloader valve sends pressurized water into the bypass, the water is sent via a hose to the inlet, where it is recycled through the pump. This water circulates through the pump repeatedly, becoming pressurized and depressurized until it is released through the gun or wand. 

Although this bypass provides excellent protection for the pump and its components, it should not be left cycling for an extended period. Friction in the crankcase generates heat, and as water is continuously cycled through it, that heat is transferred to the water. If the water becomes too hot, it can damage seals and other internal pump components. 

To counteract this, the trigger on the spray gun or wand should be squeezed occasionally to release the water before it reaches excessive temperatures. This action draws in fresh, cooler water and prevents damage to the pressure washer.