Made me think about just how much pressure is needed for various jobs, so I found this online:
"Pressure and Water Flow
How much pressure and flow (water volume) are required to get your job done properly and efficiently? The work value of a power washer is decided by two factors, pressure and flow. Most people only consider pressure and disregard the equally important flow of the unit.
Pressure washers can be more correctly called power washers, since the ability of the unit to wash, or its power, is determined by both pressure and water volume.
Pressure is measured in pounds per square inch (PSI) and determines how much power the unit has to clean surfaces. The PSI of a washer determines how effectively it break the bonds of the debris to the surface being cleaned.
Water volume, also known as the flow of the unit, is measured in gallons per minute (GPM) or litres per minute (LPM.) Flow is the amount of water being thrown at the surface being cleaned. The water flow of the washer affects the time it takes to clean a surface. A washer with a higher flow rate will take less time to clean than a lower flow unit.
The following examples list common tasks for pressure washers and the pressure needed to do them:
Car wash: 700 to 1,000 PSI
Cleaning decks / house sidings: 1,000 to 1,500 PSI
Heavy duty equipment and agricultural uses: 2,000 to 3,000 PSI
Concrete surfaces and heavy industrial uses: 3,000 + PSI
Agricultural applications rarely need 3,000 PSI. A few years ago most farmers were purchasing 3,000+ PSI units but they have now opted for 2,000 to 2,500 PSI units that have higher flow rates. This is because when cleaning a barn the debris being cleaned can be removed from surfaces fairly easily, but must then be flushed from the surface and moved."
2007 Winnebago 26P