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Pressure Washer PSI vs. GPM: What’s the Difference?
Here’s an easy, no-pressure lesson
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Pressure washer GPM, or gallons per minute, measures water flow rate, while PSI measures water pressure force against the surface you're cleaning.
A higher GPM means more water flows from your nozzle per minute, helping you cover large areas faster without increasing pressure on delicate surfaces.
The best choice for your project depends on the surface type and cleaning intensity needed, balancing water volume against pressure to avoid damage.
Hiring a local power washing professional provides helpful guidance on matching the right equipment to your surfaces, keeping your home safe from pressure damage.
If pressure washing your patio or vinyl siding has been lingering on your to-do list for far too long, perhaps it’s because of the pressure of picking the right tool for the job. There are two measurements to know: pounds per square inch (psi) and gallons per minute (GPM). Keep reading to learn why having the right amount of both is important for the best results.
What Are the Differences Between PSI and GPM?
Here’s what you need to know about the key differences between the psi and GPM of pressure washers.
| Type of Difference | PSI | GPM |
|---|---|---|
| Measure | Force of water | Flow rate |
| Result | Pressure on surface | Amount of water |
| Usage | Tough stains | Large areas |
Pressure Washer PSI vs. GPM: Differences in Measurement
PSI, or pounds per square inch, measures the pressure or force of the water coming out of the pressure washer’s wand or spout. The higher the number, the stronger the flow. As an example, a run-of-the-mill garden hose delivers 50 psi on average.
GPM stands for gallons per minute, which is the water’s flow rate. To get a sense of GPM, think about your showerhead, which is also measured in GPM. The average showerhead has a GPM of 2.5.
Result Differences
A higher PSI means a more intense flow of water. It’s what puts the pressure in “pressure washer,” which you need in order to wash off stubborn dirt and stains. The psi is like the pressure washer version of a scouring pad—it’s best reserved for stubborn messes on surfaces strong enough to withstand the blast.
GPM, on the other hand, is all about the amount of water coming out of the nozzle. The higher the GPM, the more water there is shooting out per minute, regardless of the pressure behind it.
In short, if you need more power, go with more psi. If you simply want more water, go with a higher GPM.
Usage Differences
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What does your cleaning project need: more pressure or more water? A higher psi is better for stubborn stains on smaller areas, but this is only true if the surface can handle that added pressure. High-psi machines are used in industrial or agricultural applications because the surfaces or equipment can handle the water blast.
Tough stains on softer surfaces, like a wooden deck, will benefit from a machine with a higher GPM. Otherwise, the pressure will cause it to splinter or chip. If you’re using a cleaning solution in addition to your pressure washer, then it’s also a good idea to go with a higher GPM machine because there’s more water coming out of it to wash it all away. More gallons per minute will get the job done faster, especially if you’re working on a large area, like a long driveway.
If you’re not sure whether or not something you want to clean is safe to pressure wash, call a pro for advice. A power washing pro near you can give you tips or handle the entire job so that you avoid a big mess from a DIY gone wrong.
How Cleaning Units (CUs) Relate to PSI and GPM
Photo: carlofranco / iStock / Getty Images Plus / Getty Images
When deciding on which pressure washer is right for the job, you might see another measurement called cleaning units, or CUs. A CU is the number you get by multiplying the psi rating by the GPM rating.
For example, a pressure washer with 2,000 PSI and 3.0 GPM has 6,000 CU. However, a pressure washer with 3,000 PSI and 2.0 GPM also has 6,000 CU. So, while CUs are a good way to determine a pressure washer’s capabilities, they don't tell the whole story. That’s why it’s more important to focus on psi and GPM separately to ensure you get the job done right.
Frequently Asked Questions
Pressure washing services reviews from real Angi homeowners in Columbus, OH
4.9★ avg. • 16 total reviews
- Austin Y.
I would recommend this company to anyone! He showed up on time, was friendly, completed a very difficult repair on our dryer vent cover, was responsive, and pricing was extremely fair and competitive. I would have him back to do any of our repairs or cleanings without hesitation!
U.S.A. Dryer Vent, LLC - David B.
The technician was very professional and friendly. He answered all my questions and was very thorough. He left the fireplace area very clean . He inspected from the roof and advised me as to other work that might need to be done. There was no pressure there. I was very satisfied with the...
Supreme brick & chimney - Kellie G.
Mary Cleaning Service is fantastic! The entire team is professional and pay a great deal of attention to detail. They do such a thorough job of cleaning my house. I would definitely recommend!
- Diane C.
The workmanship is perfect, I did not have any complaint with that. It was the brick I chose not matching the brick that want I to use. There was a problem with discoloration of the brick. I thought that the rain was gonna wash it off but it didn't. I call them. All communication was coming...
Bone Dry Roofing & Masonry - Cincinnati - Dana M.
I purchased the "Big Deal": $199.00 for exterior pressure-washing of one- or two-story home up to 2,000 square feet. They cleaned the siding only. I wasn't aware when I bought the Big Deal that they would not do any other surfaces other than the siding (i.e. sides of the gutters or stucco). I...
Complete Home Services - Laura R.
We noticed that there was a light brown residue in the drip tray of our stackable washer dryer. We have a Lowe's warranty so contacted them to arrange a service call. They arranged an appointment for 2 days out with Capital City. Capital city then called the next day saying they were not...
Capital City Appliance Service - Gary T.
From the initial sales presentation to the installers final clean up, this project was a total pleasure. Gary Coper, sales consultant, showed up exactly on time and provided an informative, no pressure description, of every material and step required to complete the remodel. We were always in...
Simple Bath & Simple Kitchen - Victoria R.
They were prompt, careful and thorough. I have also had them wash interior floor to ceiling windows which were perfect.
Technicare Carpet Cleaning - William B.
The work went great! Couldn't ask for better. Joel set a work start date. About the time of the storms that may have been associated with Sandy. He was half a day late. They set up on a Thursday. On Friday they had a full crew at work. By Monday they were finishing up. Now, the best...
NJW Construction
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