The high-pressure water shooting out of the spray gun of a pressure washer is due to the effects of several key components of the pressure washer with the most important being the pressure water unloader valve.
Knowing how the unloader valve of your pressure washer operates could help you to make better use of the machine. It could also help you to prevent damage to the pump, gun/spray wand, or hose.
Like every other valve, the pressure washer unloader valve regulates the flow of water in the pressure washer, which creates the high-pressure water you use to blast surfaces clean.
When the trigger on the spray gun is depressed, the unloader valve diverts the water flow through the bypass allowing for adjustments on the pressure of your machine.
Every pressure washer is made up of a two-part value system consisting of the unloader valve and the trigger on the spray gun. Through this valve system, water is directed into the bypass of the unloader and then back to a header tank or into the water inlet side of the pump.
The unloader valve re-circulates the water back to the inlet side of the pump or back to the header tank when the trigger is shut off.
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What is the Importance of a Pressure Unloader Valve?
The main function of the valve is to avoid extreme pressure buildup in the pump so that water redirected from the pump passes through the unloader hose and is recycled through the power pump.
The pressure will continue to build if the unloader valve is not present to redirect high-pressure water in the pump. If this continues, it will exceed the machine’s PSI (pounds per square inch) limitation and damage the pump and other components.
Several problems that could arise from a faulty or misadjusted unloader valve that I’ll talk about later. You must apply the right measures when making adjustments to the valve.
Related: Best Pressure Washers Under $600
How a Pressure Washer Unloader Valve Works
A pressure washer unloader valve diverts the flow of water in the pump into the bypass port. The valve works in a way that relieves pressure from the pressure washer.
You can increase or decrease the water pressure coming out of the nozzle through the unloader valve.
To do this, you need to know how the unloader valve works in the first place.
There are two types of pressure washer unloader valves; each has its operating system and adjustment system.
The trapped pressure unloader and the flow-actuated unloader function more like opposites with an increase in one reflecting a decrease in the other.
A trapped pressure unloader valve reacts to changes in pressure. When the trigger on the spray gun is released, there will be an increase in pressure. This will cause the unloader valve to open sending the water back to the inlet side of the pump.
A flow-actuated unloader also reacts to pressure. When the flow of water is stopped, there will be a buildup of internal pressure. This happens when the trigger of the gun is depressed. The water will be diverted through the bypass and back to the inlet side of the pump.
How to Adjust a Pressure Washer Unloader Valve
Unloader valves come as a spring that can be adjusted to control how much pressure it will allow to buildup in the pump before redirecting water. You can increase or decrease this pressure by adjusting the spring.
Since the two types of unloader valves have different working systems, they also have different ways in which the spring can be adjusted to bring about pressure changes.
Before getting started, note that adjustments should only be done in small increments or decrements to prevent pressure from building too high or going too low.
While adjusting, attach a pressure gauge to the pump before the unloader to help monitor pressure changes. Also, keep the machine running and the trigger wand pulled while you make adjustments
Note that improper adjustment or handling could cause damage to the unloader valve and other related components.
How to Adjust a Trapped Pressure Washer Unloader Valve
To adjust a trapped unloader valve, press the trigger and loosen the screw from the body of the valve to ease the tension in the spring. Release the trigger to check if the unloader is working. Press it again to allow the system to build its operating pressure at that adjustment. If you’re not okay with it, you can tighten the bolt while the trigger is pressed.
This process should be repeated until the desired pressure is achieved. Always check the pressure gauge with each adjustment.
How to Adjust a Flow-Actuated Pressure Washer Unloader Valve
Adjusting a flow-actuated unloader valve works similarly. Tightening the adjusting nut will increase the bypass pressure while loosening it will decrease the bypass pressure.
While making adjustments, ensure that the spike pressure is no more than 200 PSI above the operating pressure or this could damage the machine.
Overheating the Bypass
The bypass in the pressure washer can become overheated when water cycles for too long. The excess heat is due to the friction in the crankcase as the water is continuously cycled through it. This heat is transferred to the water, thus raising the temperature of the water. If the water gets too hot, it could damage the pump. To prevent this from happening, occasionally discharge water by squeezing the trigger of the spray so that the pump gets a fresh and cooler supply of water.
Causes of Pressure Problems in a Pressure Washer
The following are some of the major causes of pressure washer problems.
Worn-out Trigger Wand
While the unloader valve handles everything related to pressure change, it might not be the only culprit if you’re experiencing a gradual loss of pressure in your pressure washer. This could sometimes be as a result of a worn-out trigger wand. Replacing the trigger wand would solve this problem in such a case.
Wrong Parts
If you’ve changed the unloader valve of your pressure washer recently, check to make sure you bought the right one for the machine. Consider buying directly from manufacturers when buying parts for your machine.
Incorrectly Adjusted Loader
Tightening or loosening the spring of the unloader valve will set the pressure at which the unloader will divert water away from the pump. This process might sound simple, but it could be tough for someone with zero knowledge about the operating system of pressure washers. Incorrectly adjusting the unloader, especially without a pressure gauge and above 200 PSI than the normal operating pressure will lead to pressure problems and sometimes damage to the pump or unloader.
Unloader Needs to Be Replaced
Sometimes a faulty unloader could lead to a gradual loss of pressure in a pressure washer. You may need to fix or replace the unloader if you’ve checked other parts of the machine and adjusted the unloader but still notice no change.
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