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pressure washer PSI vs GPM

pressure washer PSI vs GPM

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When shopping for the best pressure washer, you must know how much power you need. It also determines whether you can go with an electric unit or need to switch to gas power. Do you want to know what pressure washer PSI and GPM are, what’s the difference between them and which one matters the most? Then this guide is for you.

pressure washer psi vs gpm

Pressure washer PSI

Most people are familiar with pressure washer PSI, or pounds per square inch. It measures how hard the water hits and helps you understand its ability to dislodge trapped debris.

As you can guess, the higher the PSI, the more power the water has. In many cases, the bigger the better. However, too much stress can be a bad thing. It’s possible to start peeling paint off cars, rip wood from deck boards, and even start other types of damage with moderate power and a narrow nozzle. You can manage the impact of the water by using a wide nozzle angle that still gives you the removal you need.

Remember, the effective use of a pressure washer doesn’t solely depend on high PSI. It’s about achieving the right balance between PSI and GPM – but more on that later. Now that we’ve explored PSI in depth, stay tuned as we delve into GPM in our next discussion.

Pressure washer GPM

The term “gallons per minute” (GPM) is used to measure the flow of water produced by a pressure washer.

Unlike PSI, there is no risk of damage caused by excessive water flow. The higher the GPM rating, the faster an object will move after a force loosens it.

Using a pressure washer with incorrect GPM can result in inefficient cleaning. A low GPM may result in longer cleaning times because it simply won’t rinse away dirt and debris as quickly. Conversely, too high a GPM can lead to water waste and potential water damage.

How do I calculate GPM?

The formula for finding GPM is 60 divided by the seconds it takes to fill a one-gallon container or tank (60/sec = GPM). For example, A gallon container fills in five seconds. 60/5 = 12 GPM. (60 divided by 5 is equal to 12 gallons/minute.)

Pressure washer PSI vs. GPM

It is the combination of PSI and GPM that gets the job done. The PSI vs. GPM head-to-head winner will depend on the task to be performed. Do you regularly clean chewing gum off your sidewalk? Are you dealing with tar stains every time you clean? You are looking for a high PSI rating. 

Are you working on standard home improvement projects like siding, windows, and decks? A high GPM will help you complete the job faster.

Identifying your ideal PSI (low or high) is a good start for most homeowners. Once you have the desired PSI, look for a higher GPM number to achieve better performance. When you are considering two or more pressure washers with the PSI range you are looking for and want to know which is better, consider the formula for cleaning units. It multiplies the two values together to give you an estimate of the total cleaning capacity.

Let’s take a look at an example of two pressure washers.

Pressure washer 1:

  • PSI rating = 3200 PSI 
  • GPM Rating = 2.5 GPM
  • Cleaning units (CU) = 2.5 x 3200  = 8000 CU 

Pressure washer 2:

  • PSI rating = 3300 PSI 
  • GPM Rating = 2.4 GPM
  • Cleaning units (CU) 3300 x 2.4 = 7920 CU

Although the second pressure washer has a higher PSI, the first has a higher cleaning unit. They are close, but comparatively, you will do the job more efficiently with a machine with a lower PSI.

Choose the PSI and GPM that suits your cleaning needs

  • Type of cleaning: The nature of the cleaning task plays an important role in determining the appropriate PSI (pounds per square inch) and GPM (gallons per minute). Light tasks like washing your car or outdoor furniture typically require lower PSI and GPM, while heavy-duty tasks like cleaning a concrete driveway or stripping paint require higher PSI and GPM.
  • Surface to be cleaned: The material of the surface to be cleaned is another key factor. High PSI can damage delicate surfaces like vehicle exteriors or wooden decks, so a pressure washer with a lower PSI and GPM is suitable. On the other hand, resilient surfaces like concrete or brick can withstand and may even require higher PSI and GPM to clean effectively.
  • Budget considerations: Pressure washers with higher PSI and GPM ratings generally cost more. Evaluate your budget and consider cost-effectiveness based on your specific needs. Remember, it’s not always about getting the highest PSI or GPM, it’s about finding the right balance for your cleaning tasks.

Examples of PSI and GPM requirements for different cleaning tasks

Light cleaning tasks typically involve those that require a delicate balance of power to ensure effective cleaning without causing damage. These tasks are common in residential settings and include activities like washing cars, cleaning patios, or rinsing outdoor furniture.

Light TasksInstructionsPSIGPM
Car WashingDelicate spray pattern, nozzle a foot away.1600-19002.0-2.5
Patio CleaningStart low, increase as needed, wide spray.1800-20002.3-2.5
Furniture RinsingWide spray, avoid cracks/joints.1600-18002.0-2.2

Medium cleaning tasks require a step up in power and precision compared to light tasks. These tasks often involve surfaces that can withstand more pressure without damage, such as concrete floors or home sidings.

Medium TasksInstructionsPSIGPM
Dirt RemovalMedium spray, gradual pressure increase.2000-23002.5-2.8
Siding CleaningStart top-down, angle nozzle.2200-25002.8-3.0
Fence WashingMedium spray, steady distance.2000-23002.5-2.8

Heavy cleaning tasks typically involve the removal of stubborn, ingrained dirt or substances like paint or graffiti. They can also include industrial applications such as equipment cleaning.

Heavy TasksInstructionsPSIGPM
Paint RemovalNarrow spray, gradual pressure increase.2500-28003.0-3.3
Graffiti EradicationMedium spray, gradual pressure increase.2600-30003.2-3.5
Equipment CleaningWide spray, steady distance.2800-30003.3-3.5

The right pressure washer with correct PSI and GPM can tackle any cleaning task. Contact our team for personalized advice on selecting the perfect pressure washer for your needs. Act today!

bison pressure washer series


In conclusion, understanding PSI (Pounds per Square Inch) and GPM (Gallons per Minute) when using a pressure washer is crucial for both efficiency and safety. These two measurements directly impact the cleaning power of your machine and can significantly influence the outcome of your cleaning tasks.

Call to action

BISON is ready and willing to assist you in making an informed choice that will get your surfaces sparkling clean in no time. Visit our pressure washer series at https://www.bisonindustry.com/high-pressure-washer/ for more information on various pressure washer models, their PSI and GPM specifications, as well as tips on how to effectively use them.

BISON pressure washers have a good balance of PSI and GPM out of the gate thanks to the deliberate pairing of motor and pump. As you go up in PSI, you usually go up in GPM as well. 

If you’re still wondering about the best combination, we recommend starting with something in the range of 3000 – 3500 PSI/2.0 – 2.5 GPM . These pressure washers are suitable for most homeowners, as they work efficiently and are affordable. 

FAQs about pressure washer PSI and GPM

As a guide, a concrete driveway with moderate dirt, around 3000 PSI, and 4.0 GPM will make the best, most effective, and time-efficient clean. Pressure washing your driveway can help reduce wear and tear on the concrete and enhance the appearance of your home without breaking the bank. Pressure washers can remove mildew, grease, and stains from driveways.

Price is the biggest drawback of pressure washers with high GPM ratings. However, you get what you pay for in more efficient, effective cleaning.

Another thing to consider is that higher GPM pressure washers can be more challenging to control. You could accidentally damage surfaces if you’re not used to pressure washing with a high GPM pressure washer.

Finally, high GPM pressure washers require more maintenance than low GPM pressure washers. You must clean the filter more often and ensure the pump is properly lubricated.

A high GPM pressure washer is good if you are willing to pay more for a pressure washer and are comfortable with more maintenance. But if you need more time to decide whether you’re ready for a high GPM pressure washer, it’s best to start with a low GPM pressure washer. Of course, you can always upgrade later.

Typically, contractors or professional cleaners prefer a higher GPM machine over PSI because they use cleaning solutions to loosen dirt rather than relying entirely on PSI. Basically cleaning up the mess. The higher the GPM, the faster it will clean larger surfaces.

Pressure washers used for commercial work require higher GPM. Contractors use special chemicals to help with cleaning, so they need to pay more attention to rinse power and get a commercial pressure washer with a high water flow.

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