How a Pressure Washer Unloader Valve Works

Did you know that you can’t stop pressure washing without turning your machine all the way off? Well, you can, but you shouldn’t.

Without a pressure washer unloader valve, dangerous pressure can build up if you step away to take a phone call, chase your dog, or chat with your neighbor. 

Why? When you let go of the spray wand trigger, the engine is still on, but no pressure is released. This high pressure buildup can cause serious damage to your machine. 

An unloader valve is an essential investment if you’re regularly using your pressure washer. Using this tool will help you avoid costly repairs or replacement by regulating the system pressure. 

What is a pressure washer unloader valve?

Essentially, an unloader valve is a safety switch. It sends pressurized water into a by-pass by cycling it from the outlet side of the pump to an inlet or water tank. This process depressurizes the water and prevents pressure from building up while the pressure washer machine is idling. 

How does it work?

Think of this trapped pressure unloader as a relief valve. Depending on the type of unloader valve you have, it’s activated by an increase in pressure or a decrease in flow.  When you release the trigger gun, the valve activates its spring and ball-check mechanism, sending the water into by-pass.

The spring and ball mechanism diverts the flow of water from the spray nozzle and sends it in a continuous cycle from the outlet side to the inlet side of the pump system. This happens until you pull the wand trigger again. 

When you activate your pressure washing wand again, the flow actuated unloader will switch off and redirect the water to your nozzle.

Why do I need one?

First, for safety. Usually, your turn a power washer on and off with a switch. Depending on your hose length, you could be pretty far away from your machine. 

Any number of events could quickly pull you away from your pressure washing job. You might not have time to run back and turn your pressure washer off. 

For example, you may get an important work call, an emergency could happen, or your dog gets out. Unexpected events happen all the time! 

A pressure washer unloader valve allows you to safely step away from your machine if you need to.

Without an unloader valve, the water pressure continues to build up in the nozzle, potentially causing a very unsafe situation.

The increase in pressure – without an unloader valve to regulate it – could cause the water pressure to go over the PSI limit, potentially damaging your pressure washer’s pump.

Using an unloader valve ensures that you’re operating the machine safely and extending its life.

While the increased safety is certainly a perk, the unloader valve is also great for ease of use. It allows you to adjust the operating pressure of the spray gun while on the job. 

Pros and cons of using an unloader valve for your pressure washer

Pros

• Increases Safety: A pressure washer unloader valve prevents built up pressure from exploding out of the pressure washer wand and injuring you, someone else, or damaging the project you’re working on.

• Avoids Damage: In the event of an emergency, you can safely let go of the pressure wand trigger and address the emergency without worrying about damaging your machine.

• More Convenient Use: You can adjust the pressure stream easily with a pressure washer unloader valve.

Cons

Pressure Issues: Installing or adjusting the valve incorrectly could lead to pressure issues. Pressure issues result from incorrectly tightened or loosened springs in the unloader valve. Additionally, using an incompatible valve could cause a decrease in pressure.

Heat Buildup: Letting the water circulate for too long could cause heat buildup, leading to damage.

Pro tip: Don’t leave your pressure washer in bypass mode for too long. If it is left for too long, the water could heat up to extremely high temperatures that cause softening of your o-rings and corrosion of your pump.

Unloader Valve FAQs 

Q: How do I know if the unloader valve needs replacement?

There are a few signs that will tell you if you need to replace your unloader valve. Look out for the following: 

• Water leaks
• Loss of pressure in the machine
• The pressure washer engine is stalling
• The thermal release valve emits steam

While you want to check for other issues like blockages, troubleshooting your pressure washer may point to the unloader valve as the culprit. 

Q: How do I adjust the unloader valve?

First, set up for adjustment

1. Make sure your pressure washer is on a flat surface.
2. Start the engine and keep it at 3700 rpm before load and 3400 rpm under the load.
3. Remove the nylon lock inside the unloader valve.
4. Shut off the pressure adjusting nozzle.
5. Remove the washer and spring from the unloader valve. Do you see the threaded piston with two lock nuts?
6. Grab a wrench and lock the two nuts.
7. Apply 3 threads off the bottom and put the washer, spring, and nut back in place.
8. Clip the pressure between the HP hose and the pump. Keep an eye on these when you move to the unloader valve adjustment.

Second, adjust the unloader valve

1. Turn on the outlet valve on the pressure washer. Do not turn it off until only water is flowing out of the house. The main goal is to remove all the air.
2. Tighten the pressure spring, but keep an eye on the pressure gauge assembly. 
3. Pull the pressure washer wand trigger until you reach maximum pressure. The pressure spike should be around 6 to 9 percent. 
4. If the pressure is spiking higher than 10 percent then adjust the nuts until you see the pressure spike hit below 10 percent. 
5. If you’re still not seeing below 10 percent then you might need to remove the adjustment knob, washer, and spring and adjust those. 
6. Twist the unloader multiple times to break it in.
7. Replace the washer, spring, and knob.
8. Check the gauge one more time before screwing everything back into place. 
9. Make sure to put the cap back on the unloader valve.

Q: How do I prevent the water from overheating?

Spray small amounts of water from the wand to stop the water from constantly circulating in the water inlet. You want to prevent the hot water from getting over 140 degrees Fahrenheit or 60 degrees Celsius.

Wrap-up on pressure washer unloader valves

Everyone with a pressure washing machine should have an unloader valve for two reasons:

• Safety 
• Ease of use 

These pressure regulators depressurize water and send it into a bypass cycle so that you can safely step away from your machine in case of an emergency. 

Second, pressure washer unloader valves allow you to adjust water pressure easily while pressure washing with your machine. 

Remember to make sure that your pressure washer unloader valve is installed correctly and is compatible with your pressure washing machine.