How Pressure Washer Unloader Valves Work

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You don’t need to know all the parts of a pressure washer to use it. But the unloader valve is one component that is worth learning. It is included in all pressure washers and there’s a good reason why Without it, the machine won’t function properly and will suffer serious damage.

A pressure washer unloader valve redirects water flow from the wand. It is a safety mechanism to lower pressure when you stop pressing the trigger.

The unloader valve keeps water flow and pressure in check. If you remove the valve or it stops working, water pressure will rise quickly and damage the pressure washer.

How Unloader Valves Work

These valves are safety features and work the same way. When a pressure washer runs. the pressure increases until it reaches the limit set by the unloader valve.

As soon as it hits that stage, the unloader valve changes the water flow from the spray wand into an inlet.

This bypassing process is an important safety element because high water pressure carries a risk for the machine and the operator.

If you release the spray gun but don’t turn off the motor, the pressure is still there. An unloader valve brings the pressure down even if the engine is running.

Some unloader valves are triggered by reduced flow, while others by increasing pressure. Both are activated when you let go of the spray wand.

When you do so, the valve automatically goes into bypass mode. The water flow is redirected to a tank or inlet until you pull the trigger again.

Safety tip: squeeze the trigger every half a minute or so, more often is fine. The system generates a lot of heat when in bypass mode due to the water. This can damage the pump if it goes on too long.

By pulling the trigger every 20-30 seconds, the system deactivates bypass mode, reducing flow speed, friction and temperature.

Benefits of Unloader Valves

Safety. The most obvious is that it is a safety mechanism. If you take out the unloader valve, the pressure will keep going up.

This will cause serious or permanent damage on the engine. If the pressure exceeds the pressure washer’s PSI limit, it can destroy the pump. You can check this out if you want to find out how pressure washer pumps work.

Longer lifespan. Unloader valves protect pressure washers and keep them running smoothly. That’s why this mechanism is found in all pressure washers today.

Ease of use. Unloader valves make pressure washers easy to use in two ways.

First it allows you to safely release the spray wand. A call from the boss, the burgers are overcooked, the cat is on the computer, a lot of things can happen that require you to drop the spray gun.

With an unloader valve you can do this without worry. No need to go to the machine to switch it off. The unloader valve mechanism kicks in the moment you let the trigger go.

Second, unloader valves allows you to adjust the pressure. It just makes the job a lot easier.

How to Adjust Pressure Washer Unloader Valves

If your pressure washer isn’t performing as you expect, adjusting the unloader valve might help. Here’s how you do it.

  1. Place your pressure washer on an even surface.
  2. Turn it on if you haven’t done so. If under load, set the RPM at 3500 or 3700 before load.
  3. Take out the nylon lock on the unloader valve. Refer to the manual for the right wrench size.
  4. You’ll see a washer and spring on the valve. Remove them.
  5. Use a wrench to lock the nuts on the piston.
  6. Off the bottom you should set set three threads.
  7. Put the nut, washer and spring back.
  8. Next step is clipping the pressure between the pump and hose.
  9. Open the outlet valve. Keep it open until all the air has gone out and only water comes out.
  10. Adjust the spring and tighten it.
  11. Squeeze the spray gun to the highest pressure. The maximum should be 9%. If it goes higher, tweak the nuts until the pressure is below 10%.
  12. If maximum pressure is still 10% or higher, readjust the spring, washer and knob.
  13. Once the pressure is below 10%, put everything back in place.

This video shows you the process.

Signs of a Damaged Pressure Washer Unloader Valve

Little to no water pressure is the most common sign of a damaged unloader valve. This can happen for other reasons but a broken unloader valve is one possibility.

Other possible signs of a damaged unloader valve:

  • Pressure washer starts and stops
  • The engine stalls
  • Steam comes out of the thermal valve
  • Pressure still increases when you let go of the spray gun

Safety Tips

  • Unless you know the exact steps, let a professional examine and replace the unloader valve.
  • An incorrect installation can cause pressure problems. This issue occurs if the springs are too tight or loose.
  • Unloader valves are not universal. You can only install a valve that’s compatible with your pressure washer.
  • Heat rising. Don’t stay in bypass mode for too long as the temperature increases. Too much heat damages the pump.
  • Always keep an eye on the pressure when adjusting the valve. A lot of potential problems can be avoided this way.

Can I Replace Unloader Valves?

Unloader valves are some of the most durable parts of a pressure washer. I’ve been using pressure washers for a long time and rarely see an unloader valve break down.

If your unloader valve is damaged, can you replace it? It depends on what type of unloader valve your pressure washer is.

Make sure the unloader valve is designed for your pressure washer. The CarbPro 310924003 Unloader valve kit for instance, is compatible with several Simpson and Coleman pressure washers.

Internal unloader valves. If the unloader valve is built into the pressure washer, replacing it is going to require some effort.

Most built-in unloader valves are in the pump housing. Unless you’re comfortable disassembling some pressure washer parts, it’s best to let a professional handle this.

External unloader valves. These are outside the pump housing and easier to find and replace.

This video demonstrates how pressure washer unloader valves are installed.

Frequently Asked Questions

Does pressure loss mean the unloader valve is damaged?

There are many reasons why a pressure washer loses pressure, and a non-working valve is one of them. if you release the trigger but the water isn’t diverted, the valve is definitely broken.

Water leakage is another symptom. If your pressure washer isn’t running like it used to, there could be a valve issue.

Can a pressure washer run without an unloader valve?

No. These are safety mechanisms and pressure washers will not function without them. If the valve isn’t working, the pressure washer will not function properly.

Don’t attempt to use a pressure washer with a damaged valve. If you have to leave the pressure washer suddenly and you’re far from the switch, the unloader valve serves as a safety switch.

if the valve isn’t working and you fail to turn the machine switch off, the pressure will keep going up and damage the pump.

Can I use any type of unloader valve?

No. Pressure washers are designed to work with specific types of unloader valves. Some are built in and others are external.

Choose the one that fits with your pressure washer. Check the manual or manufacturer site if you’re not sure.

How often should I replace unloader valves?

A quality unloader valve should last for years. If you buy a good pressure washer like the Simpson CM61083 there’s a good chance you won’t ever need to replace it.

Which is better, a built in or externally mounted unloader valve?

Both types perform the same function. Built-in valves are better protected since they are incased. But they are more difficult to replace. Externally mounted valves work well too but not all pressure washers support it.