How Does a Pressure Washer Work? Pics & Diagram

Published by: | Updated: July 1, 2023
JCS Refresh How Does A Pressure Washer Work

A pressure washer requires a lot of upkeep to ensure it’s ready when you are.

As a homeowner, buying one for routine tasks throughout the year is smart, but before spending, a question comes to mind – is it worth the investment?

To answer this, we’ll discuss how a pressure washer works and how many resources they use, so you can better understand the inner workings.

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About The Author

Meet the expert behind this article. 



Co-owner & Service Director

Hey there, I’m Cody. 

A decade of residential and commercial pressure washing led me to start JCS Refresh. Now I can share my knowledge with folks like you. 

Reading from Washington State?

Our services range from Arlington to Seattle.

Visit our pricing page for specials.

Quick answer: How do pressure washers work?

Particularly great for outdoor cleaning, pressure washing is what its name implies: it uses high-pressure water to remove dirt easily. 

Sometimes, machines use hot water (referred to as power washing) for stains that are tougher to clean. 

Here’s how a pressure washer works:

The power comes from a gas-fueled or electricity-operated engine that powers the water pump. 

The water supply, typically supplied by a garden hose, is sped up by the pressure from the pump. 

When the trigger is pulled, water combines with air, turning into high-pressure water, and exits through the nozzle.

Parts of a pressure washer

Below are the primary parts of a pressure washer.


The pump adds pressure to regular hose water, turning it into a powerful cleaning spray.

How does a pressure washer pump work?

The pump is the heart of the machine because it is responsible for pressurizing the regular hose water. Depending on the model, it is powered by a gas engine or an electric motor.

Pumps come in various types, but they all work by drawing water from the supply and converting it into high-pressure water that exits through the hose. 

For example, if you’re using soap the pump mixes them with water before releasing through the hose.

JCS Refresh - How Does A Pressure Washer Work - Pump
Here is a pressure washer pump.

Gas engine or an electric motor

Depending on the model, a gas or electric motor drives the pump to generate pressure.

Unloader valve

The unloader valve depressurizes water and allows you to leave the machine safely if needed. 

Additionally, it can adjust the pressure based on how you intend to use the machine.

How does a pressure washer unloader valve work?

In contrast to the pump, the unloader valve depressurizes and functions as a safety switch. These valves work by cycling pressurized water back to the inlet, depressurizing the water, and preventing pressure buildup when the unit is idling.

JCS Refresh - How Does A Pressure Washer Work - Unloader Valve
This is the unloader valve on a pressure washer.
JCS Refresh - How Does A Pressure Washer Work - Turbo Nozzle
This is a pressure washer turbo nozzle.

Turbo nozzle

A turbo nozzle can be added to increase force and clean tough stains.

How does a pressure washer turbo nozzle work?

A turbo nozzle rotates the water, turning it into a powerful stream. It is connected to a nozzle tip and is attached to lances and wands. 

They hit the surface at multiple angles and break down dirt and grime, which is why these machines clean so well.

Soap injector

The soap injector allows you to apply soap or cleaning chemicals under low pressure.

How does a soap injector work on a pressure washer?

Soap is sucked out of its container by suction when the soap injector restricts the water flow through the nozzle, lowering the water pressure. However, soap injectors can break from time to time, so be on the lookout for clogs and other issues.

JCS Refresh - How Does A Pressure Washer Work - Soap Injector
This is a pressure washer turbo soap injector.

Pressure washer gun

The gun, also called the spray gun, is a device at the end of the hose that directs the water flow.

How does a pressure washer gun work?

The pressure washer gun directs the water to the surface being cleaned and connects the hose to the solution or soap.

It allows you to target specific areas, making it useful for hard-to-clean areas that would otherwise be impossible to reach with a wand. 

JCS Refresh - How Does A Pressure Washer Work - Spray Gun
This is a pressure washer gun, aka, spray gun

Inlet hose

Also referred to as the garden hose, an inlet hose supplies water to the pressure washer.

JCS Refresh - How Does A Pressure Washer Work - Inlet Hose 1
Here is Cody connecting the inlet hose to the water supply.
JCS Refresh - How Does A Pressure Washer Work - Inlet Hose 2
Then he connects the other end to the pressure washer.

Pressure hose

The high-pressure water from the pump flows through the pressure hose, which is stronger than a regular garden hose. 

Pressure hoses are made to handle four times the pressure rating of the unit, so they don’t burst.

Watch as Cody connects the inlet hose to the pressure hose.
JCS Refresh - How Does A Pressure Washer Work - Pressure Hose 2
Here's another view of the pressure hose.

How does a pressure washer surface cleaner work?

Surface cleaners are excellent attachments typically used on hard, flat surfaces.

It operates by connecting to hose. Once connected, high-pressure water is sprayed through the bottom of the surface cleaner. Small nozzles on the spinning arm’s head clean the surface evenly and without leaving streaks.

JCS Refresh - How Does A Pressure Washer Work - Surface Cleaner
Here's Cody putting that surface cleaner to work.

Pressure washer diagram

A machine starts by drawing cold water from the water supply and passing it through a filter and the pump, where high-pressure water is produced and regulated by the unloader valve.

The high-pressure washer then goes to the lance, the gun, and exits through the nozzle. 

Additionally, a cleaning agent can be added to the water flow, either upstream or downstream of the pump.

Review the diagram below to see this in action.

JCS Refresh How Does a Pressure Washer Work - Pressure Washer Diagram

Technical diagram from Comet.

What are pressure washers used for?

You might be surprised at how helpful these machines are for cleaning various outdoor surfaces, equipment, and even the most unusual items. 

Here are five primary uses for a pressure washer:


Cleaning your driveway with a pressure washer is the most effective way to eliminate unsightly stains and harmful growth. Additionally, it enhances your home’s curb appeal and leaves your driveway refreshed and clean.

JCS Refresh - How Does A Pressure Washer Work - Driveway Before and After
Before and after pressure washing a driveway really matters.


Fences are your home’s exterior barriers and are vulnerable to weather and temperature changes, causing dirt, algae, mildew, and mold to grow. 

If you plan to revitalize your fence, pressure washing is the best way to prep your fence for staining. You don’t want dirt sticking to your fence before applying a fresh coat.

To learn more, visit our page about fence cleaning services.


Pressure washing brick—the right way—produces a beautiful and clean facade. 

However, the PSI setting for brick is not the only thing to be mindful of when cleaning. 

To ensure you don’t damage the surface permanently, keep a proper distance, pattern, and use the correct cleaning agent.

JCS Refresh - How Does A Pressure Washer Work -

Decks and patios

When exposed to the elements, mold, and mildew can multiply, so cleaning your your deck is essential. 

Pressure washing can also eliminate dirt, dust, and other unwanted things tracked in from the outside by people walking all the time.

To learn more, visit our deck cleaning services page.

Other things

  • Windows
  • Garage floors
  • Sidings
  • Gutters
  • Concrete floors
  • BBQ Grills
  • Garbage Cans
  • Boats
  • Lawn Mowers
  • Dog Houses
  • Other outdoor equipment
JCS Refresh - How Does A Pressure Washer Work - Gutter Cleaning
Look at Cody blasting dirt and grime from those gutters.

To learn more about various pressure washer uses, read our full guide – what is a pressure washer used for?

Frequently asked questions

The following are some frequently asked questions surrounding this topic.

Are pressure washers waterproof?

Although pressure washers with high IP ratings are safe in wet conditions, we do not recommend using your unit during heavy rain, storms, or extreme hot and cold weather conditions. Doing so will cause corrosion and damage to the unit.

Do pressure washers need a hose?

Yes. Running hose water acts not only as a supply but also as a coolant. Therefore, failure to use a hose will result in a dry pump, damaging the unit.

How do pressure washers get water?

Pressure washers are connected to a water supply, typically a garden hose.


If you’re a homeowner who intends to use your pressure washer regularly, rather than storing it in the garage, it’s an excellent investment.

However, like any other good machine, they are expensive, require maintenance, and some surfaces require more skill. 

If that’s the case, you might consider hiring an expert (like us) to tackle areas of your home that need a refresher.

Thanks for reading!