With a pressure washer, you can rid your siding, deck, and driveway of dirt and grime, strip paint off of a deck or house, wash away congealed oil and grease, disinfect, and rid surfaces of mold. They are truly amazing and a great tool to have when a garden hose just isn’t doing the job. However, it is important to know what you are buying, especially in terms of power. Too little power and the washer won’t be effective, too much power and you can potentially ruin whatever object or surface you are cleaning.
How is power measured?
A pressure washer’s power is measured by two factors: pounds per square inch (PSI) and the gallons per minute (GPM). A washer’s PSI rating reflects the maximum amount of pressure that it can discharge. A higher PSI means more cleaning power. GPM refers to the amount of water outputted by a washer in the span of one minute. A higher GPM means a faster cleaning time (usually).
You may also see the phrase “cleaning units,” which refers to the combined total of the GPM and PSI when they are multiplied together. For example, a pressure washer with a PSI of 2000 and a GPM of 2.2 would equal a washer with a cleaning unit rating of 4400.
Pressure Washers and PSI
Pressure washers range from 1000 PSI to 50,000 PSI, though most websites only sell units with up to 4000 PSI. (No matter what residential job you have to do, you will never need 50,000 PSI of power. Those types of models are on huge projects, like pressure washing bridges) Of course, the question is how much power is needed for the job you want to do or the jobs you plan to do in the future.
Unfortunately, there is no set guide. During the course of research for this article, the writer consulted many different guides and sources and they all had different recommendations for what PSI was best for certain jobs. In general, however, most seemed to agree that light residential cleaning, such as washing automobiles, sidewalks, outdoor furniture, stairs, and small areas of moderately dirty flooring, patios, and decks can be efficiently cleaned with a light duty model with 1500 to 1900 PSI. Larger areas, like large decks, patios, and garages, fences, driveways, and siding require a more powerful, medium duty unit with 2000 to 3000 PSI. Units that have over 3000 PSI are most commonly used for commercial jobs and big projects, such as stripping paint from a building
GPM
A unit’s GPM will correlate with its PSI. You will likely never see a 1750 PSI washer with 4.0 GPM, mainly because force dictates how fast water moves; a higher amount of force means greater speed, which results in more water output. Usually, a unit’s GPM is close to its PSI amount with the decimal point moved three places to the left. For example, a pressure washer with 1400 PSI will likely have a GPM around 1.4.
