Glossary of Terms
Pressure washer terminology and keywords


Ultimate Washer pressure washer glossary of terms provides you with a collection of textual glosses and specialized terms with their meanings. Use the following terminology and keywords as your pressure washer dictionary.


Adjustable Pressure Regulator
Varies the pressure of the high-pressure spray.

Adjustable Spray/Multi-Reg Nozzle
Some models are equipped with a Multi-Reg nozzle that allows you to adjust the spray angle by turning the tip (0º to 45º degrees disperse). In addition, such nozzles will allow a chemical solution application at a low-pressure.

Axial Cam
A device (cam) used to transform the rotary motion of the motor/ engine into the reciprocating motion of a pump's pistons. Axial Cam usually has fewer parts in its system and that is why such units are less expensive.

The axles need to be strong enough to support the weight of the machine and long enough to keep the balance of the machine.

Belt Drive
Belt driven units use pulleys and belts to slow the speed of the pump. Where the engine spins at 3,800 RPM the pump will be slowed to 1,400 to 1,900 RPM depending on the pulley and belt set up. This system ensures long pump life because the bearings do not get as much wear and the pump is isolated from the heat of engine, being separated by the belts and pulleys. The disadvantage of this system is there is some loss of efficiency due to the additional friction from the belts and pulleys. Plus there is more maintenance required adjusting the belts. However, all other things being equal the belt drive unit should provide for the longest pump life.

The shock of thousands of bubbles collapsing inside the pump quickly pitting metal surfaces and seals. Cavitation, also known as starving the pump, is caused by lack of water at the inlet of the pump.

Ceramic vs. Nonceramic Plungers
The plunger is the moving part of a pressure washer pump that travels back and forth between rubber seals to create the flow and pressure of a pressure washing system. The material that is used on all industrial grade pumps is ceramic. This material has excellent properties that allow it to be extremely smooth — extending the life of the seals. Ceramic also does not wear. Non-ceramic plungers will wear and reduce the life of the seals.

Chemical Injector
The chemical injector, which comes standard with many of our pressurewashers, allows soap or chemical to be injected into the water stream making cleaning even faster and easier. It works in harmony with the variable pressure wand to control the flow of the chemical. For units with a straight through wand, the operator must switch to a soap nozzle to draw chemical with the injector.

Cleaning Units
Cleaning abilities achieved by the pressurewasher. Use simple formula to determine the total cleaning units produced by your machine: cleaning units (CL) = pressure (PSI) x water volume (GPM).

Direct Drive
In direct drive pressure washer systems the pump is connected directly to the engine. So, the pump spins at the same speed as the engine, usually around 3,800 RPM. This system has the advantage of being simple, with few moving parts; therefore, less expensive. The disadvantage is by having the pump spin as much as the engine the bearings get more wear and tear, reducing the life span of the pump.

Engine (Diesel, Gas, Electric motor or Hydraulic power source)
The engine, motor or outside hydraulic sources are the energy sources that drive the high-pressure pump. Which is better for you? In short, gasoline models are for outdoor use and are much more portable. Electric models are not as portable, but are quiet and ideal for indoor use. Diesel engines are more durable and have longer lifetime.

EZ Start Adjustable Unloader
EZ Start unloader eliminates pressure in the pump while starting the engine making the unit to start easier; less damaging to starter motors especially on electric start engines.

The frame is critical because it supports the working components of the powerwasher. Our frames will not warp, bend or crack under the heaviest demands. They are also painted with a powder coat for longer life in all conditions and minimal risk of rusting. Many of our models come on stainless steel frames.

Frame (Powder Coated)
The heavy-duty powder coated frame is designed to be compact, portable and able to withstand years of rugged and punishing use.

Gearbox Pumps
Gearbox drives contain a gear reduction box between the pump and the motor; thus, running at approximately 1600 rpm, or half the speed of direct drive pumps. This slower speed results in lower maintenance expenses, because of less frequent seal and valve replacement.

Ground Fault Current Interrupter (GFCI) protects user from accidental electrocution (for electric powered pressure washers only). More information on ground fault current interrupters.

Gallon Per Minute. More water per minute can mean faster cleaning, especially when washing off materials like mud and road tar. The following chart shows how more gallons per minute can reduce your cleaning time. (The times shown are estimates only. Variation in job size, conditions and operator skill will affect the results)

20 Minutes
18 Minutes
16 Minutes
14 Minutes
12 Minutes
10 Minutes
8 Minutes
6 Minutes
4 Minutes
2 Minutes
2.5 GPM
3.5 GPM

Most pressure washers come with at least one handle either chrome or painted. Some models come with front and some with rear handles for convenience in moving and loading into the back of a truck, as well as to give added protection to the vital components.

High Pressure Outlet
Connection for high-pressure hose.

High-Pressure Pump
The pump draws water from an external source (usually a garden hose attached to a faucet) and pushes it with such force to produce pressures as high as 3000 and 5000 PSI. In comparison, a garden hose creates 40-50 PSI. Some pressure washers come with industrial-grade triplex (three plunger) pumps and some with duplex pumps (two plungers).

The nozzle is the restriction at the end of the wand that creates the pressure. Nozzles have different spray patterns that can affect the width and strength of the spray. For instance, the 40-degree (white) nozzle delivers a flat spray of about 40-degrees. There's also a 25-degree (green) and the most popular 15-degree (yellow) nozzles. Caution operators about the 0-degree (red) nozzle. It can cut into wood and cause damage.

OHV Technology improves efficiency, cools running, and reduces emissions. Same as 'overhead valve', an improved way to control exhaust and intake valves on internal combustion engines.

An industrial, more durable version of the OHV engine.

Pressure (PSI)
The unit for pressure is PSI (pounds per square inch), which actually determines how much pressure is directly applied on the surface being cleaned. The pressure that is delivered by the machine is directly responsible for breaking the bond between the debris and the object being cleaned. Our models typically have a pressure range from 1000 to 5000 PSI.

Pressure Washer Gauge
Ultimate Washer analog pressure gauges combine both a chemical seal and a pressure gauge into one unit. Diagram elements are circular shaped, convoluted membranes that are clamped around the rim between two flanges. The measured media (power washer) exerts a force on the diagram. A metal pushrod welded to the bottom of the diaphragm transmits the deflection of the diagram to the linkage. The linkage, in turn, translates the lateral motion of the push rod into a rotational motion of the pointer.

Pressure Washer Hose
There are two types of pressure hose. Wire-braid high pressure hose can be rated for up to 4500 PSI. Non-marking pressure hose is gray in color and it can be freely used on any surface without worries of possible rubber marks left behind. They are also usually rated for up to 4500 PSI.

A method of eliminating air from a pressurewasher so that starting the engine is easier.

Same as revolutions per minute. The amount of revolutions (turns) an engine makes in one minute.

Safety Relief Valve
The safety relief valve is the designed weak point in the pressure washer. If the unloader malfunctions, the safety relief valve will open and relieve system pressure safely.

Sewer Line Definition
A drain or passage to carry off water and filth under ground; a subterraneous channel.

Stainless Steel
The stainless steel frame, turbo tip, schedule 80 coil, and other parts and accessories are made of an alloy of steel chromium and sometimes another element (as nickel or molybdenum) that is practically immune to rusting and ordinary corrosion.

Storage Rack
Provides storage for hose, gun and cleaning solution bottles.

This is the range of temperature over which device may be safely used; the temperature range which the device has been designated to operate.

Thermal Relief
A technique used to reduce the build-up of high temperature water within a powerwasher pump caused when the spray gun trigger is closed. Cycles water through pump when water reaches maximum water temperature. Some of our models have pumps designed to work with the water temperature of 145ºF, 160ºF and some as much as 180ºF. Warm water will discharge from pump onto ground. This system prevents internal pump damage.

Trigger Gun
The pressurewasher gun controls the flow of water. The flow is activated simply by squeezing the trigger and stopped when the trigger is released.

Turbo nozzle or turbo tip
A device used to increase the effectiveness of high-pressure water, by spinning a narrow stream of water in a circle at a high speed.

A device used to relive the water pressure within the pump whenever spray flow is blocked. It allows the engine or motor to continue running even when the operator lets go of the trigger on the spray gun and stops washing. It diverts the pressure, that would build up without the unloader, by taking the water from the exit side of the pump and loops it back to the inlet side in a continuous "bypass" mode. The unloader also returns the flow of water to the gun when the operator is ready to clean again.

Running the unit in bypass mode for extended periods of time increases water temperature, as the water is re-circulated. This hot water can damage the high-pressure pump. The majority of our units come equipped with a thermal pump protector that dumps this hot water and brings in cold water, thus preventing damage to the pump.

There are two common types of wands--the variable pressure (or dual lance) wand and the straight through wand. The variable pressure wand allows the user to simply twist the handle on the wand and reduce the spray pressure. If the chemical injector is attached, the soap or chemical will automatically be injected into the water stream after the pump when the pressure is turned down. Simply turn the pressure back up and the soap injector stops drawing soap. In addition to the convenience, this is the best way to apply soap because it never passes through the pump. Many soaps and chemicals are harmful to a high-pressure pump.

Water Flow (GPM)
The unit for water flow is GPM (gallons per minute), which is actually the amount/quantity of water used in a one-minute period. The volume of water determines how fast the dirt can be removed from the surface once the bond between the debris and the surface has been broken. The unit with higher GPM level will require less time to clean; consequently, a washer with the lower GPM level will entail more time for the same job performed.

High-grade power washers come with tubed, pneumatic tires instead of hard rubber or plastic tires. Tubed pneumatic tires are used for longer wear and easier maneuvering of the powerwasher on most surfaces. Additionally, pneumatic tires absorb vibration, which saves wear and tear on the working components.

Work (HP)
There is one more factor to remember when buying power washers, which are sometimes equally as important as pressure and water flow. That's work. The unit for work is HP (horsepower), which actually determines how much power the machine has to clean the surface. Typically the more horsepower a machine has will allow for higher pressures or volumes or a combination of both. Larger engines are more powerful and therefore more capable of finishing the job quickly.