In a properly designed high pressure washer, the high-pressure pump system pushes the water supplied from an outside source through the pressure washer at a carefully selected pressure and flow rate. The pump is a piston or plunger type that pushes water through a cylinder and then out through a hose and spray nozzle. The pump is driven by an external electric motor or engine. Higher output flows at lower output pressure or higher output pressure with lower output flow rate is achieved by the pressure washer design by sizing the components in the pressure washer.

The key decision on what flow rate (GPM) and pressure (PSI) to have with your pressure washer is as follows:

1. For cleaning smaller surfaces that are loaded with grease, dirt and grime and particularly if it is hard to scrape off, higher pressure at lower flow rate is usually best.
2. For cleaning larger surfaces that are loaded with light, dirt or film, but relatively easy to remove, higher flow rate with lower pressure is usually best to cover the surface faster.
3. Most surfaces to be cleaned are usually some combination of A or B above and not strictly one or the other. The way to handle this is to either use a pressure washer with a higher capacity in both modes that can easily be switched back-and-forth (higher cost) or to choose a model that can handle a wide range of flow and pressure by easy adjustment. Note: Most pressure washers are in this category with a mid-range price.

The above descriptions required judgment and selection. If you wish you optimize your selection with enough capacity and lowered cost, please contact Spartan MFG, Corp. customer service at 336-996-5585, Eastern time. An expert application engineer will help you to optimize your choice and there is no obligation for this.