Pressure Washer - Power Washer: Glossary
Cavitation - Cavitation is caused when air gets into your pump - damaging it as the pump expands and contracts. It's also known as "starving" the pump.
Chemical Injector - Standard with many pressure washers, a chemical injector allows the soap or chemical to be injected into the water stream, making cleaning even faster and easier.
CU (Cleaning Unit) - Cleaning units are the actual measure of power washer performance. They are calculated by multiplying the water pressure measurement (PSI - pounds per square inch) and the water flow measurement (GPM - gallons per minute). The product is the Cleaning Unit, or CU.
Engine (Gas or diesel, electric motor) - The engine or motor is the energy source powers the high-pressure pump. Gas models are for outdoor use and are more portable. Electric models are tied to a power source, but are quiet and easy to store inside, since fumes are not a concern. Diesel-powered engines are the most durable, and have the longest working life.
Frame - The frame supports the working mechanics of the power washer. They can be constructed of aluminum or stainless steel, and are often powder coated to increase resistance to corrosion.
GPM ( Gallons per Minute) - THis is also termed the "water flow rate," the measure of the volume of water going through the system and out the nozzle. GPM is a vital measurement in the equation that determines a pressure washer's cleaning power (CU). A rate of "3" or more is a good GPM rate, though anything above a "2" is fully adequate for most residential jobs.
High-Pressure Pump - The pump draws water from an outside source (usually a garden hose attached to a faucet) and pushes it with an amount of force to produce pressure as high as 3000 to 5000 PSI (a garden hose used by itself operates only at 40 to 50 PSI.) Some pressure washers come with industrial-grade triplex (three plunger) pumps and some with duplex pumps (two plungers) - with the best quality pump plungers made of ceramic material.
Nozzle - It's the nozzle, the restriction at the end of the pressure washer wand, that creates the pressure. Nozzles have different spray patterns that can affect the width and strength of the spray. For instance, a 40-degree nozzle delivers a flat spray of about 40 degrees. A wider spray reduces ability to cut through dirt.; a zero-degree nozzle provides a jet of intense power. Fan sprays of 40 degrees and more are generally used for simple washing chores and 360-degree rotating nozzles are also used for some specific cleaning applications.
PSI (Pounds per Square Inch) - The unit of measure for pressure, and in the case of pressure washers, the measurement of the strength of the spray coming out of the nozzle. A typical garden hose releases water at a pressure of about 40 PSI, a light-duty electric washer runs about 1000 to 1200 PSI and a heavier-duty consumer-grade gas model operates from about 2800 to 3500 PSI. Industrial-strength washers can exceed 5000 PSI.
Pressure Washer Hose - There are two types of pressure hose: (1) wire-braid high-pressure hose which is strong enough for up to 4500 PSI. (2) Non-marking pressure hose is gray or yellow and can be freely used on any surface without the risk of leaving black marks; usually approved for up to 4500 PSI.
Safety Relief Valve - The safety relief valve is the designated weak point in the pressure washer system. If the unloader mechanism malfunctions, the safety relief valve will open and relieve accumulated pressure safely.
Trigger Gun - The pressure washer gun controls the flow of water. The flow is activated simply by squeezing the trigger and stopped when the trigger is released - sort of like a squirt gun!
Unloader - This is one of the most important, yet trouble-prone protective devices on your pressure washer. It is used to relieve the water pressure within the pump whenever spray flow is blocked. The unloader lets the engine (or motor) keep running, though the operator may have let go of the trigger and stopped washing. The built-up pressure is diverted by the unloader, which "unloads" the pressure by taking the water from the exit area of the pump, channeling it back to the inlet area. The unloader also returns the flow of water to the gun when the operator is ready to clean again.
Wand - There are two common types of wands (lances): the variable pressure (or "dual lance") wand and the straight through wand. The variable pressure wand let the operator twist the handle on the wand and reduce the pressure.