To find a machine that best suits your application the two things you must consider is the gallons per minute (GPM) and the pressure per square inch (PSI). Factoring in both of these will ensure that you will get the best cleaning performance from a machine that you purchase. PSI is the number that most people look at when purchasing a pressure washer but GPM is just as important and is often overlooked.
The GPM is other known as the amount of water being projected towards a surface. The GPM can also be referred to as the flushing power used to clean a surface. This flushing power is used to get rid of heavy solids that might consist of dirt, clay, manure or any other large particles. An easy way to think of GPM is the water that comes out of your garden hose; there is a lot of flow but not a great deal of pressure.
Then there is the PSI that a pump can produce, the PSI is the pressure that is forced on or into a surface when cleaning. The more PSI you have the more aggressive your spray against a surface will be. Without PSI water would just fall onto a surface and not cut any dirt or grime but if you have too much pressure and it is not used correctly you can cause damage to the surface being cleaned. For instance many metal cutting companies will use machines that produce 10,000 psi at low amount of GPM to seamlessly cut through 2 inches of metal. If you were to use too much pressure on a surface such as concrete it will take off what we call the skim coat that give concrete its smoothness on the surface. If you use too much pressure on a wooden deck it will cause the water to cut into the surface and the wood would splinter.
In most situations the more PSI and GPM you have will determine how fast your cleaning project will go. If you are a commercial cleaner that uses the machine everyday and all day long you would want as much PSI and GPM that you could get that won’t exceed what your water supply puts out. On the other hand, if you are a residential user that only uses a power washer a couple times a year then a larger machine wouldn’t be needed unless you want to get your cleaning projects completed fast or want to have a little bit bigger then that pesky neighbor that has every tool imaginable.
Make sure when choosing a power washer you look into both the GPM and PSI. Many brands will solely advertise the PSI that a power washer has and 9 times out of 10 is going to be over rated to the actual pressure that it produces. In addition, when you see a machine that is rated with higher psi then more than likely they reduced the GPM of the pump to produce more PSI. Like stated before the GPM of a machine is just as important as the PSI, a machine that produces 4 GPM will clean two or more times faster than a machine that produces 2 GPM. So if you still don’t know what the best machine for you might be see chart below.
|1000-1800||2.0-2.4||Homeowner/light duty||Cars, boats, patios, gutters|
|1900-3000||2.2-3.0||Homeowner/heavy duty||Houses, farm equipment, pools, sidewalks, truck fleets, steel buildings, driveways|
|3100-5000||3.0-5.0||Commercial Use||Industrial, heavy grease, large particles, stubborn stains in concrete, removing algae, stripping paint|
For many commercial and industrial users it may also be necessary to use a machine that creates its own hot water in order to breakdown the bond that greases, oils and road films make to a surface.
If you feel that your power washer is not doing the best job on a given application there is a good possibility that it isn’t the right machine to use for your cleaning job. Before you go out and purchase a new machine consider the fact that using a cleaning detergent or a specific accessory can not only speed up the cleaning process but also provide for a better result in the end.