Pressure washer shoppers often ask how much pressure they really need from a pressure washer, and the answer is: it depends on your project. The pressure put out by a power washer is measured in PSI (pounds per square inch), and the PSI requirements can vary based on what you need to clean.
For example, it'll take a lot less pressure to clean dirt and salt from your vehicle than it will take to clean oil stains from your garage floor. Another factor that's equally as important, but not often considered, is the gallons per minute rating (GPM). This measures how much water your pressure washer puts out per minute, and more water equals faster cleaning.
When determining what range of PSI you want from a pressure washer, there are two general schools of thinking. The first is, buy for the pressure you'll eventually want because you can dial the pressure down enough to handle any lesser project, and you'll benefit from the 'buy it right and buy it once' effect, instead of later upgrading down the road.
If, for example, you want a pressure washer to clean your car, but later realize you want to use it to clean your driveway, remove stains, and strip paint, the ranges of PSI recommendations are very different, and you might be disappointed when yours isn't powerful enough to handle the job efficiently.
On the other hand, if you're never going to exceed 2,500 PSI for your projects, then you can save some money by choosing a 2,600 PSI pressure washer over a 4,000 PSI pressure washer. Remember that pressure ranges are variable - in other words, there isn't always a noticeable difference between 1,500 and 1,600 PSI, and you should always start with lower pressure recommendation and work your way up, instead of starting at the upper end of a recommended PSI range and risk damage to whatever you're cleaning.
The list below has some recommended PSI ratings for a few common household cleaning projects.
While water pressure provides the power to break up stains and dirt, water volume is what flushes that broken-up filth away.
Essentially, the more water that moves through your nozzle in a minute, the faster you'll be able to clean. Greater GPM (gallons per minute) cleans quicker because there's more flowing water present to lift and carry away the dirt.
Imagine a garden hose that is flowing. On its own, you've got flow for wetting, but not pressure for cleaning. Now apply your thumb over the end of the hose, and you can wash clumps of dirt off your driveway or sidewalk. This principle applies to PSI and GPM: if you can combine the pressure of your thumb (PSI) with the volume of the hose (GPM), you'll have a great cleaning tool. Pressure washers allow you to do just that, combine high pressure with high volume to clean stubborn surfaces in record time.