Pressure is measured in pounds per square inch, or PSI. The higher the pressure a washer can produce, the more power it has to shift stubborn dirt, gunk, moss and other tenacious stains. Many of the washers I tested produce only a few hundred PSI of pressure, which is enough to shift dirt, remove surface stains from asphalt and concrete or rinse gunk off the siding of your house, but without damaging the material itself.
The Sunjoe has a lot of cleaning features in a single package with five included nozzles.
Nozzles
All of the washers I tested come with a variety of nozzles that spread the water in an arc to wash a wider area, ranging from 5 to 50 degrees. They also come with a turbo nozzle, which produces a single stream of water sprayed in a spinning helix, producing a cone-shaped spray that offers high pressure for washing, but with less risk of damage to the material being blasted.
Most of the nozzles that come with these pressure washers are designated by the angle of the fan that they spray: the wider the angle, the wider the cleaning coverage, but the less pressure the water has. They are usually color-coded, with green for the smallest angle, then orange and white for the widest. As a general rule, use a smaller angle (10 to 25 degrees) for removing stubborn gunk of a small area, then shift to a larger angle, upwards of 30 degrees, to shift the loose debris.
The best place to start is with the makers of pressure washers call a turbo nozzle, which releases a single thin jet of water in a rotating arc, like a rotating lawn sprayer, but more focused. This can offer the benefits of both a small-angle nozzle (focused power) and a wider nozzle that sweeps the dirt away.
Zero degree nozzles
Here you can see the width of the fan made by the yellow 15-degree tip versus the 0-degree red tip.
Zero-degree nozzles, which are red-colored and release the full pressure of the washer in a single, focused stream, are controversial because they can be very dangerous. That concentrated beam of water moving at hundreds of miles an hour can injure you, tear apart wood, strip paint, crack bricks and score concrete. So, many washers don’t include them: in the pressure washers we tested, only the Ego included one as standard. Most other manufacturers offer one as an optional accessory, but I don’t think most people need one.
The SunJoe also includes a zero-degree nozzle, which is colored red (for danger) and produces a single intense stream of water. That nozzle is also available as an optional accessory for several of the other washers.
As an uncle once told me, with great pressure comes great responsibility. Use a zero-degree nozzle and a powerful washer on your deck, and it can tear up the wood, blasting away the sealant and wood surface to let in water, which can produce cracks and rot. Use it on your car, and it can turn a tiny paint chip into a rust patch by getting under the top layer of paint and lifting it off. Use it on your siding, and it can strip the paint or even crack the panels, causing leaks in your home.
Material
To illustrate the problem, I attempted to pressure wash a concrete slab, a piece of deck wood and a brick using the 5-degree nozzle on the Ego Power Plus 3,200, the most powerful of the washers I tested in its turbo mode.
Using the turbo nozzle on the EgoPower+ 3200 caused damage to the wood.
All three materials were marked by the powerful flow, but the wood was the worst, with part of the wood torn away to a depth of nearly half an inch. If that would have been my deck, I’d have to tear out and replace the board.
The bottom line? For general cleaning of house and car, one of the smaller pressure washers I tested like the Karcher 1800PS has enough cleaning power for most tasks and is unlikely to damage anything. If you want to keep a concrete driveway spotless or prefer your garden statuary to be shiny clean and completely moss-free, get a more powerful model like the Ego Power Plus, but be careful about how and where you use it.
Using the turbo nozzle tore the wood away at a depth of nearly half an inch.