How much water does a Pressure Washer really use? 1.24 gallons per minute (GPM). How much water does a garden hose use? 8.55 GPM. Lets look at some examples that show just how efficient your pressure washer really is!
People end up saying pressure washers are water wasting monsters! But is that true? There are some counter intuitive principles regarding pressure washer physics we should discuss.
All revolving around this one questions: How much water does a pressure washer use?
I am going to show you the facts and some calculations (sorry the math is unavoidable:) about your pressure washer.
How Much Water Does a Pressure Washer Use vs. a Garden Hose:
An average pressure washer uses approximately 8 gallons (30.28 Litres) of water per minute, or 8 GPM. Sounds like a lot?? Your average garden hose uses 12 to 13 GPM! Higher PSI = higher efficiency. Pressure washer wins.
But those averages include commercial grade equipment. Lets compare what we might find in a typical garage.
Pressure Washer Calculations (sigh…)
So, above I quoted some averages which don’t always give a clear picture. Lets talk specifics.
Take this garden hose for example:
Screw it onto your hose bib, turn on the water and you get 8.55GPM (Thank you Popular Mechanics) and lets call it 10 PSI. But nobody uses just a hose and thumb anymore so we’ll assume you screw on a gun as well and now have 5 GPM and 40PSI. You take 10 minutes and clean your drive way.
This would be the equivalent of filling up a 50 gallon trash can with water.
Now the next day, after the drive way has dried, you see it’s actually not much cleaner you decide to break out your pressure washer.
This guy’s typical operating specs will be 1450PSI and 1.24 GPM. So you spend another 10 minutes cleaning your driveway… Which is the equivalent of filling up this little guy:
So that is 50 gallons with the water hose vs. 12 gallons with the pressure washer. And the pressure washer actually got the drive way cleaner… gotta love technology:)
Pressure Washer GPM vs PSI
GPM (Gallons per Minute) also called flow rate, is the amount of water delivered by the machine in one minute.
PSI (Pound per Square Inch) refers to the amount of pressure created by the equipment.
CU (Cleaning Units) are determined by GPM X PSI. I know, ‘not another acronym!’ but CU’s come up a lot in this discussion because GPM and PSI work so closely together for how much cleaning actually gets done, so we use CU’s as shorthand.
A pressure washer with 1.3 GPM and 1700 PSI = (1.3 X 1700) = 2,210 CU
When it comes to cleaning capacity of a pressure washer, time is money. So the less time it takes to finish, the higher the efficiency is.
Not all surfaces are equal of course, and there are different kinds of contaminants. This is why some people get a great result but others don’t, even with the same pressure washer. For example, Grease on Teflon requires different cleaning pressure than grease on concrete.
Now two pressure washers might have the same max PSI but still not perform the same.
In our garden hose comparison above we highlight the efficiency of pressure washers with a lower GPM. But when comparing pressure washers, efficiency is not about less water, but about the work done. CU’s, remember PSI x GPM. Much like horsepower. Smaller engine with less horse power might be more fuel efficient, but still be under powered.
So, in addition to PSI, you need to compare GPM as well. They work together to get things clean.
Let’s assume a Sun Joe XPX 3000 pressure washer with 1.76 GPM and 2030 PSI competes with Stanley SHP2150 pressure washer with 1.4 GPM with 2150 PSI.
The Stanley has an edge over sun joe in PSI. But, do the math:
- 1.76 X 2030 = 3,572 CU
- 1.40 X 2150= 3,010 CU
The Sun Joe is the definite winner despite lower PSI. This is why you need to compare both PSI and GPM when comparing pressure washers.
A powerful pressure washer can clean any kind of surfaces with ease. Standard pressure washer ranges between 1.0-4.0 GPM and 1700-2500 PSI. I have an article on electric pressure washers for all-purpose uses.
Moreover, for only washing a car you’ll not need a heavy pressure washer. I have mentioned some pressure washers fit for car washing in this article.
How much water does a pressure washer use:
- The SunJoe SPX3000 uses only 1.76 gallons per minute.
- The monster Simpson Cleaning Megashot 3200PSI uses only 2.5 gallons per minute.
- The Paxcess Pressure Washer 2150 PSI uses only 1.85 gallons per minute.
- The Westinghouse WPX3200 uses only 2.5 gallons per minute.
- The mrliance 3500psi pressure washer uses only 2 gallons per minute
What is pressure washer psi vs gpm?
- PSI is pounds per square inch. Higher PSI means more force applied to the surface.
- GPM is gallons per minute. Higher GPM means larger the surface area covered.
- When comparing two pressure washers, multiply PSI x GPM and compare the results (also called CU’s or cleaning units).
Does a pressure washer use a lot of water?
No. Not when compared to a garden hose.