Picture of John Peters

Be Nice & Share

Proper Pressure Washer PSI: A Comprehensive Guide

Here’s an interesting fact – the water stream from a pressure washer can cut you. It’s not uncommon for workers and homeowners to be slashed or bruised by pressure washers.

Pressure washer PSI (pound-force per square inch) can reach insane numbers. The typical home pressure washer can go as high as 4000 PSI, and it only takes 2,901 PSI to punch through the skin.

Power washers that reach 40,000 PSI can even puncture steel.

Pressure washers can damage both you and your property, so it’s essential to know what PSI is and proper safety precautions. You also need to know the appropriate pound-force per square inch suitable for specific materials.

We’ve put together a comprehensive guide to getting you started on what you need to know about pressure washing below.

Pressure Washer PSI, GPM, and CPU

There are two distinct measurements that you need to know when handling pressure washers. There’s PSI or pound per square inch and GPM or gallon per minute.

PSI measures the force that water sprays out of the pressure washing machine. The PSI is what muscles through all the stuck-on dirt and grit. GPM is the volume of water that the pressure washer expels per minute.

The pounds per square inch represent the speed water sprays out the power washer. The gallons per minute are how much liquid is coming out every minute.

CPU or cleaning power units dictate how quickly your washer can clean things. If you’re interested in figuring out the CPU, you need to multiply the PSI by the GPM.

The higher a washer’s CPU, the faster it will clean surfaces.

A washer with 1,000 PSI with 7 GPM will have a CPU of 7,000. Now let’s compare it to a power washer with a 5,000 PSI and a GPM of 2.

The second washer’s CPU is 10. Despite the lower CPU, the second power washer will clean the fastest.

Still, CPUs can be somewhat misleading. Two washers can have matching CPUs, and one may clean much better than the other.

PSI VS. GPM: Which Is Better?

Professional cleaners often consider GPM the most crucial measurement for power washers. Odds are a professional is using a cleaning solution to clean dirt, grease, and grime.

The solution combined with the volume of liquid released at once will make their job much faster.

Even without the cleaning solution, GPM is what’s cleaning objects. The PSI breaks the bond between dirt and items, but your power washer’s gallons per minute washes it away.

The more water that comes out of the washer nozzle each minute, the faster you can clean up. There’s a catch to using power washers with higher GPM, though.

If you’re using more water by the minute, then that’s more money you have to pay on your water bill.

Pressure Washing Safety Precautions

We’ve discussed how dangerous power washers can be and what power washer PSI levels are best for specific situations.

Now, we’ll talk about pressure washer risks and the safety steps you should take to keep yourself safe while using a washer.


In 2014 over 6,000 people were injured and hospitalized while using pressure washers. Fourteen percent (about 800 people) needed further hospitalization for their wounds.

It can be easy to think of your pressure washer as a glorified water hose, but many washers are electrical or gas-powered, which can be dangerous if you don’t know what you’re doing.

  • Leaving wounds untreated can lead to infection or even amputation
  • Electrocution may occur if the power washer is mishandled
  • Gas-powered engines can cause carbon monoxide poisoning
  • The pressurized water can knock over nearby objects


You should never make the mistake of thinking that power washers can’t be dangerous simply because you’re working with water.

You can take many precautions to ensure that you don’t hurt yourself or others while working. There’s a list of guidelines you should follow to keep safe whenever you’re using a washer.

  • Do not try moving or using things with the pressure washer
  • Always inspect pressure washer parts before use
  • Make sure power washers and outlets are electrically grounded
  • Do not remove grounding prongs from power washers or cords
  • Use heavy-duty extension cords and keep them out of water
  • Use extension cords rated for use in wet areas
  • Keep extension cords away from items you’re washing
  • Do not use cut or spliced power or extension cords
  • Test the ground fault circuit interrupter (GFCI) before use
  • Have an electrician check the pressure washer if it trips a breaker
  • Wear insulated, slip-proof, rubber-soled boots
  • Wear gloves to protect the hands
  • Wear goggles to prevent eye injuries
  • Do not allow children to use a power washer

Pressure Washing PSI Guide

You wouldn’t use the same PSI setting for your golf cart or car that you would for your patio. “Patio PSI settings” need to be higher because dirt works its way into wood more deeply than metal.

The deeper dirt and grime get into an object, the more water pressure you’ll need to remove it.

You may have realized by now that what you’re doing determines the PSI you should use. However, your specific task also determines the kind of pressure washer – gas or electric – you’ll need.

Gas washers tend to be more potent than electrical ones. A gasoline pressure washer is ideal for heavy residential, commercial, and industrial purposes. Electric washers are better for residential tasks.

Power Washer Classifications

There are four pressure washer classifications:

  • Light Pressure – Rated at 2,000 PSI or lower
  • Medium Pressure – Rated from 2,000 to 3,000 PSI
  • High Pressure – Rated from 3,000 to 6,900 PSI
  • Ultra-High Pressure – Rated from 7,000 to 50,000 PSI

Light pressure and medium pressure washers are best suited for household tasks. If your car or boat needs washing, then a light-duty pressure washer can handle the job.

A medium-duty pressure washer is strong enough to blast greasy, grimy stains from residential areas. Homeowners can safely clean sidewalks, concrete driveways, decking, and siding with a 2,000 to 3,000 PSI washer.

Professional washers often utilize high-pressure power washers to clean larger commercial and industrial areas. These diesel or gas-powered washers rid large swaths of concrete of filth and peel away paint and tough rust spots.

An ultra-high pressure washer or water blaster is used to wash enormous structures and large buildings. You won’t likely see a water blaster outside of an industrial or engineering environment.

Ultra-high pressure washers are too powerful to be used for any other purpose.

Want More Pressure Washer Advice?

Pressure washing can come off as deceptively simple and safe.

However, you need to know the ins and outs of pressure washing before deciding to use one – luckily, we’ve got your back.

Now that you’ve got information about pressure washer PSI, safety tips, and general power washer PSI levels – do you want to learn more?

Check out some of our TCHEM services for more information on how we can help with your power washer.

Be Nice & Share

Hungry for more pressure washing tips? Subscribe to our Newsletter!

We’ll send you fresh tips each month to improve your skills and boost your business. 

More Articles

6 tools every professional pressure washer needs


We would love to send you our FREE list of the 6 Must haves that every professional pressure washer should have on their truck at all times.