A pressure washer is a mechanical tool that produces a high-pressure water stream powered by an internal combustion or electric motor. It is most commonly used for cleaning dust, mold, algae, dirt, and similar types of build-ups, on outdoor surfaces such as:

  • Driveways
  • Decks
  • Roofs
  • Outdoor house walls

Or basically, any surface made of:

  • Concrete
  • Vinyl (PVC)
  • Brick 
  • Asphalt
  • Aluminum

There are a couple of “gray” areas that can be pressure-washed but should be approached with caution, such as cars and roofs.

Regarding cars, it’s safe to use a pressure washer if its pressure per square inch (PSI) is below 1500. However, most electric pressure washers operate at around 1900 psi which is enough power to damage the paint or other parts of your vehicle, so caution is advised.

This is also true for roofs; as they weaken over time, pressure-washing can cause damage to the roof tiles, especially the roof shingles, which are usually made of asphalt. 

How Does a Pressure Washer Work

Since water cannot be compressed, applying pressure will push it outward in every direction. Therefore, when channeled through a single nozzle, it creates a powerful stream which is the base principle of every pressure washer system.

A pressure washer consists of two central parts; a power source (engine) and a water pump, followed by the water inlet and the hose as the secondary components.

The power source can be either an electric motor or a gasoline engine. Electric motors are usually fitted into smaller models with less power capacity, while gasoline engines withhold more force.

On the other hand, the pump can be an axial or a triplex pump which uses three plungers to regulate the water.

Once you turn on the pressure washer, the starter engages the drive cup on the flywheel and rotates the crankshaft. The crankshaft engages the piston, which moves up and down. Their interaction starts off the ignition process.

Magnets are built into the flywheel, which, when engaged by rotation, creates a magnetic field that induces electricity. Meanwhile, the piston travels down the cylinder opening the intake valve and forming a vacuum that draws air and fuel through the carburetor, creating an intake stroke of the engine.

Furthermore, the piston goes to the top of the cylinder as the intake valve closes, making a compression stroke. That’s when the spark plug ignites the compressed air and fuel, producing a power stroke. Finally, the exhaust valve opens, allowing the combustion gasses to escape through the muffler. The engine repeats these cycles, which powers the pressure washer.

This complex process can be elaborated into a few simple steps:

  1. Once turned on, the engine powers the washer.
  2. The water pump draws water from the faucet and combines it with detergent (if added).
  3. The water is channeled through the hose into a high-pressure stream, whose power is determined by the attachment you use.

What’s the Difference Between a Power Washer and a Pressure Washer?

A power washer is very similar to a pressure washer – both will create a powerful pressurized stream of water, with the main difference being that a power washer heats up the water.

Although subtle, this element can make a big difference when cleaning particular residues, such as chewing gum, moss (hot water prevents it from growing back), or severe build-up of dirt, grease, and other types of debris. Basically, power washing is the solution when cleaning areas with extreme build-up.

However, the hot water adds additional risk to damaging the materials it cleans, especially painted surfaces, wood, and other softer materials, as it is harsher than cold water. That’s where the pressure washer takes advantage as it is better suited for lighter cleaning jobs which are the most typical for average users.

Wrapping Up

A pressure washer is a tool with very versatile usage, and it can be extremely helpful for efficiently cleaning various surfaces. However, since it is highly powerful, it can cause damage to the surface you are cleaning if not handled properly or if you use it on materials that are not suited for pressure washing. It’s best to keep it two feet (60 cm) away from the surface you are cleaning while maintaining a sweeping motion to ensure the best results while preserving the safety of both yourself and the cleaning surface.

More from PressureWashr

Jamey

Jamey is the founder of pressurewashr.com and has led testing and reviewing since 2013. He has also worked as a commercial pressure washer at a rendering plant for 3 years and has been using commercial and residential pressure washers for 15+ years. He is also a mechanical engineer and while working in the mining industry designed several turn-key light industrial vehicle wash pads.