Used by homeowners and professionals alike for tasks ranging from graffiti removal and steel hull stripping to gutter washing and deck cleaning, a pressure washer is a tool that uses a gasoline or electric-powered pump to compress water into a high-powered state. Depending on the pressure and flow of water, some machines are capable of removing paint from surfaces and blasting hardened concrete off of a steel frame. Most homeowners will never need a pressure washer to perform to that capacity, so pressure washers are classified according to application. Light-duty and heavy-duty consumer models as well as a full range of professional models are available.
Pressure Washer Design
Without getting too technical, a pressure washer is essentially comprised of a pump and a motor to power it. An inlet water port accepts a standard garden hose to supply the pump with water. To the outflow port on the pump attaches a special pressure washer hose. At the working end of the hose attaches the trigger gun or extension wand and to that a nozzle. While the pump works to pressurize water to a certain amount, the inlet orifice located on the nozzle further constricts the flow of water, adding to the pressure. Gas-fueled pressure washers use an engine to run the pump, while electric units plug into an outlet. Hot water pressure washers are a more complicated variety, for they feature an additional burner and coil system to heat water before its projected.
A pressure washer is configured in a number of ways. Common types include walk-behind units with a waist-high handle, rugged wheels and rubber stopper feet. For consumer use, rollable walk-behind as well as hand-carried models are available. Wall-mounted pressure washers are handy for fixed applications. For professional and industrial use, a pressure washer may be trailer mounted with its own self-contained water and power supply for the most mobility.
Pressure Washer Pump
Virtually all pressure washer pumps are positive displacement reciprocating plunger types. The pump of any pressure washer is its heart. Consisting of a durable manifold and crankcase, a pump features a system of cylinders and valves with plungers or pistons to compress and direct inflowing water. The best plungers are built from ceramic, while valves are often stainless steel. The design of the pump determines the water flow rate, a more important indicator of tool efficiency. The speed of the pump in RPMs, the bore of the cylinders and the stroke all influence the flow of water, measured in gallons per minute. Types of pressure washer pumps include direct and belt-driven varieties.
Power and Efficiency
A homeowner will likely not have the same power requirements as a professional cleanup crew. Consequently, consumer models feature, on average, lower max PSI and water flow rates, although heavy-duty consumer models are readily available. Power on a pressure washer is a function of its PSI rating, measured in pounds per square inch. What this figure tells an operator is the amount of pressure applied to separate a substance from the substrate or surface being cleaned. Thus, a 4000 PSI pressure washer is 4 times as powerful as a 1000 PSI unit. When measuring efficiency, look to the water flow rate. While this may be more important to professionals who calculate labor and supply costs, it is useful to consumers as well in terms of time spent and power consumed. The greater the flow of water, the more efficient the pressure washer. To calculate "effective cleaning units" of a pressure washer, multiply the max PSI by the flow rate. More ECUs means a more efficient machine.
Gas vs. Electric
In general, gas-fueled pressure washers are more powerful and efficient than electric models, although hot water electric pressure washers are an exception to this rule. Despite their greater power, gas models are outdoor use only due to their carbon monoxide emissions and may not be available in every area due to local pollution laws. They are also much louder than electric washers. In terms of pressure washer design, electric models may feature some steel components, but they are largely constructed from high-impact plastic. Gas pressure washer frames are commonly built from thick tubular steel and use rugged pneumatic tires for support. Electric models often feature built-in casters and/or handles and include an area to store accessories.
Although this is not always the case, electric pressure washers typically stay in the 1000 to 2000 PSI range and have a flow rate that usually doesn't exceed 2 to 2.2 GPM. Gas-fueled units, on the other hand, come as powerful as 5000 PSI and can feature a flow rate of up to 8.0 GPM. Most gas models are in the 2500 to 4000 PSI range even at the professional level. Gas engines used are built by Honda, Subaru, Briggs & Stratton and Kohler among others. Featured pumps include units produced by Cam Spray, Karcher, General Pump and others. In addition to gas engines, heavy-duty pressure washer pumps require oil and maintenance to keep them in good working order. Many consumer models made by Karcher, Husky and others feature maintenance-free pumps and motors.
What makes a pressure washer functional are its accessories. The most popular accessories attach to the pressure washer via quick-connect couplers. Hooking up a hose, trigger gun or nozzle is incredibly easy with these thread-less couplers. Primary accessories include a pressure washer hose, wire-braided for added strength and flexibility, trigger spray gun or lance, extension wand and nozzles. An extension wand increases the reach by up to 24 feet for high-access washing. Nozzles are specially-designed attachments used to influence the pressure and pattern of the spray. A basic pro set includes a 0-degree blaster nozzle, 15-, 25- and 40-degree fan nozzles and a black chemical or soap nozzle. Color coded for easy identification, turbo and rotating nozzles are other optional accessories. In addition, a hose reel provides an easy way to keep a hose organized and free of tangles. Reels often mount directly to the pressure washer, a wall or a trailer, but the washer itself or the reel must be sufficiently durable to support up to 200 feet of hose.
Numerous brands offer all manner of pressure washers including Karcher, Northstar, Campbell-Hausfeld, Husky, Cam Spray, Craftsman, Troy Bilt, Power Horse and many others. Pay as little as $70 for a hand-carried electric pressure washer or as much as $20,000 for a professional, trailer-mounted hot water pressure washer used for industrial applications only. These are the just the extreme ends in terms of cost. A pressure washer is available at virtually every price in between.