Operating Your Pressure Washer: Flow Rate the Key to Success



Many pressure washer owners are mistakenly led into believing an inconvenient assumption: more pressure means a cut down on cleaning time. While we at NorTex Sales & Service know this to be untrue, we want to help you understand why.

High flow rate is actually the key to calculating how long it will take to complete a cleaning job, and here’s what you need to know about it.

Pressure Washer GPM and PSI Values

Flow rate is comprised of two important values: GPM (Gallons Per Minute) and PSI (Pounds per Square Inch). This calculation is also known to many contractors as the horse power (HP) of their pressure washers. PSI is the pressure of the water and GPM is the volume of the water, measured in gallons, and also known as the flow rate.

Increasing the pressure will not lead to a faster job. Rather, the GPM value is critical in achieving a faster clean. Once your proper PSI value is established, based on the type of job you are completing, you can increase your GPM to cut down on cleaning time. Below are a few common PSIs used with various surface cleaning duties:

  • Concrete cleaning: 3,000 to 3,500 PSI
  • Car cleaning:1,200 to 1,900 PSI
  • Wood cleaning: 200 to 3,000 PSI depending on hard wood or soft
  • Trucks and tractors: PSI of at least 1,800
  • Livestock shelters: PSI of at least 3,000
  • Decks, fences, and siding: PSI of at least 2,000
  • Paint stripping, construction-site maintenance, graffiti removal: 3,200 to 4,200 PSI

What does this mean in terms of CU?

CU (Cleaning Units) is the value calculated by multiplying the PSI by the GPM values. For larger scale jobs and more frequency of use, look for a machine with a higher GPM value. These pressure washers crank out more water per gallon, which is critical in speeding up the job. Let’s take for example a professional machine with a GPM of 1 to 10. If we use a 4 GPM at a PSI value of 3,000, our CU is 12,000. If we use a pressure washer with a 3 GPM at a higher PSI value of 3,500, our CU is 10,500. The first machine is getting the job done faster.

At NorTex Sales & Service, we know clean. If you’re looking to find the right size pressure washer ideal for your business, or if you’re a homeowner who would like to know which model is best for cleaning concrete, wood, and other exterior surfaces, view our Hotsy spring line and then give us a call. We also offer a free, no obligation 15-point checkup service for your cleaning equipment!