Flow Rate is Key When Choosing A Pressure Washer

As a valuable public service, we at Just Venting are proud to take this opportunity to debunk a commonly held myth – namely that the more pressure your pressure washer washes with the better it will wash. (How’s that for a tongue twister?). The fact is, according to the technical experts at Goodway Technologies, that pressure will only get you so far, and that water flow rate plays a greater role in determining how well a pressure washer performs.

Every combination of material and contaminants has a particular pressure that is required to separate the two. Grease on stainless steel will require a different pressure than grease on aluminum, cast iron or Teflon. Similarly, paint will require a different pressure to remove it from stainless steel than will ink, chewing gum or tar. 

Once your pressure washer has reached the pressure required for a given combination of material and contaminant, more pressure won’t make the job go faster. Tim “The Tool Man” Taylor’s exhortations to use “More Power” won’t help here. But what may key to the job going faster is the use of a pressure washer capable of a higher flow rate.

Measured in Gallons Per Minute (GPM), the flow rate is really the key to determining how long a job will take. So to determine what pressure washer would be best for a given application, we proudly offer this little tip: multiply the pressure at which a system operates (measured in pounds per square inch – or PSI) by the flow rate in gallons. The resulting number will be a guide to how one system will work compared to others.

So let’s take, for example, two different pressure washers — the Goodway HPW-2000-E electric pressure washer and the HPW-2600-G gas-powered unit. The first has a flow rate of 3.5 gallons per minute at a pressure of 2,000 PSI, giving it a rating of 7,000.  In comparison,  the 2600G has a flow rate of 2.3 gallons per minute at 2,600 PSI, giving it a rating of 5,980.

For any cleaning job requiring 2,000 PSI or less, both pressure washers will do a good job getting the material clean, but the 2000E will actually get the job done faster, despite the fact that it has less power than the other system.

When you are considering what size pressure washer to buy, keep in mind that the name “pressure washer” might actually be a misnomer, since it is both pressure and flow rate you need to consider. Look at the kinds of work you need to do and how much pressure will be needed to remove the stains you want to address.

Rich Silverman
Goodway Blogging Team

17 comments


  • […] is the cheapest of the all the models offered by Dewalt. It delivers a pressure of 3200 PSI and a flow rate of 2.8 gallons per minute. The price of this model is about $800. Even though this is at the lower […]

    December 25, 2013
  • Richard Beyer

    Great advice also for purchasing a pressure washer. Many thanks!

    May 29, 2015
  • Ravi

    Great advice on buying pressure washer. I was thinking that just the PSI is more important.

    June 29, 2016
  • Randy

    Great advice, but for those of us on a well or with low supply pressure and flow, a higher washer flow rate can, as I understand it, be detrimental to performance if the supply cannot keep up with the output. I have read this is can be addressed with a buffer reservoir tank to accommodate the additional demand of a higher flow rate, but it seems my combination of a 2.5 GPH and 3600 PSI seems to be a good one. I haven’t been able to check my house flow, but the pressure is typically 35-40 PSI.

    June 28, 2017
  • […] GPM flow gives you the ability to break down the dirt and mud, and then wash it away. When you are in need of […]

    June 29, 2017
  • Richard Kenworthy

    I also have well water and my flow rate is only 1.5 Gall per minute. That’s what I was wondering if I could get a pressure washer that puts out a little more than my house flow rate.
    I rented a 2,500 psi one time and it seemed to do ok but if I’m going to invest in one I want to make sure.
    Anyone know. Thanks

    November 11, 2017
  • […] only have small cleaning projects for furniture and equipment, a washer with a 1.2 GPM to 1.5 GPM yield would suffice for your needs. A more powerful pump is necessary for more large-scale projects, of […]

    February 28, 2018
  • Rich

    My only problem is well-pumps that can’t keep up with a 3.5 gpm pressure washer. So there for you need a low gpm ratio not to wreck someone’s well-pump

    March 13, 2018
  • Victor

    Question: I purchased an 3000psi 5gpm pressure washer and not received it yet. This info is new to me and would like to know can I use this for home use. The purpose of the purchase will be to start a side job. Is this too much for home use/side jobs?

    April 13, 2018
  • Brian

    Now I’m lost? How is a pressure washer rated at 3100psi @ 2.8 gal stronger then a 3400psi @ 2.5?

    What am I not getting?

    October 10, 2018
  • Gator

    The term “stronger” is a bit misleading. The term “efficient” is probably more applicable. In your example, the 3100PSI @ 2.8GPM = 8680 rating vs. the 3400PSI @ 2.5GPM = 8500. So, assuming the material to be removed only required less than 3100 PSI to remove it, then the 3100/2.8 unit would actually make the job faster (more efficient) because of its higher GPM (it would flush the contaminants away quicker).

    December 6, 2018
  • I agree, my pressure washer gives me a number of 8100. Ok, that’s great but what does it mean? I’m looking for a round surface cleaner for my pressure washer and all I want to know is which one will work for my pressure washer. All I want is a straight answer

    March 1, 2020
  • Water Boy

    A typical water hose will produce more GPM than most any pressure washer can use. Higher GPM is needed for any seriously large or fast cleaning job,. a little 2.5 is fine for washing your car. Or cleaning off a patio etc.

    May 28, 2020
  • Water Boy

    Your well flow rate should be the “well flow: You should have a pressurized holding tank that will flow faster until it runs out.

    May 28, 2020
  • Water Boy

    It’s fine.

    May 28, 2020
  • Water Boy

    You want a direct answer as to what pressure washer to get to run a round surface cleaner. However you faile to mention exactly what surface cleaner you are speaking of. a small 12″ toy from lowes? or a 32″-60″ model?

    More is always better. Up to the maximum the unit is rated for. Otherwise you will need to move so slow that the unit will waste your time. Buy a big surface cleaner At least a 20″ then buy the maximum flow and pressure unit the it is rated for, Easy peasy.

    May 28, 2020
  • Water Boy

    You want a direct answer as to what pressure washer to get to run a round surface cleaner. However you fail to mention exactly what surface cleaner you are speaking of. a small 12″ toy from lowe’s? or a 32″-60″ model?

    More is always better. Up to the maximum the unit is rated for. Otherwise you will need to move so slow that the unit will waste your time. Buy a big surface cleaner At least a 20″ then buy the maximum flow and pressure unit the it is rated for, Easy peas.

    May 28, 2020

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