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Pressure Washing Glossary

Some common pressure washing terms

Adjustable Pressure Regulator This is a unloader valve that not only unloads the pressure but also allows you to adjust your operating pressure by just a turn of a knob on the unloader valve itself. Adjustable Spray Certain pressure washers include a nozzle that can be adjusted to allow for different angles or spray patterns just by turning your wrist. These nozzles are for homeowner type machines. Axial Pump This is a pump used to transform the circular energy of the motor or engine into a back and forth motion of a pump's pistons. Axial pumps typically have fewer parts and last only a short period of time. Belt Drive Pump Belt driven pressure washers use pulleys and belts to gear down the speed of a pump. Your engine turns at 3,750 RPM, Using the pulleys and belts the pump will be slowed to 1,450 to 1,750 RPM. By using this type of unit your pump can last up to two times longer than a direct drive pump. BYPASS Mode When you release the trigger your water goes into this mode. If you leave a machine in bypass mode for longer than two minutes you risk damaging the pump. Cavitations This is a process of starving a pump for water. Air will travel through the pump and cause it to vibrate. Frequent cavitations will damage your pump. Ceramic or Non-ceramic Plungers Pumps Ceramic plunger have a coating around the plunger giving it more rigidity. Non ceramic plungers have a shorter life and retain more heat causing premature failure. Chemical Injectors The chemical injector pulls soap or chemical into the water stream this process only works when you use your low pressure tip with a larger orifice size. You can inject pressure at high pressure although you run the risk of causing damage to your pump from the chemicals. Direct Drive Pump On a direct drive pressure washer the pump is bolted straight to the engine shaft to shaft. Your engine turns at 3450RPM and so does the pump. Building the machine this way creates a compact machine although the pump may need more attention in the long run. Effective Cleaning Units (ECU) Performance measured by a mathematical formula to determine the total cleaning units produced by your machine: cleaning units (ECU) = pressure (PSI) x water volume (GPM). EZ Start Unloader EZ Start unloader relieves pressure so starting the engine is much easier , and causes less damage to the starter on electric start engines. GPM (WATER FLOW) GPM is the scientific abbreviation for water volume or gallons per minute. When you see a machine that produces a certain GPM it also requires that same volume on the incoming side of the pump. Gear Drive Pumps This is just another means of lower the speed of a pump to make it last longer. Using a gear box in between the pump and the engine you can cut speed nearly in half on the pump side. GFCI Ground Fault Current Interrupter (GFCI) protects user from electrocution. Jetter This is a device used in plumbing and maintenance to clear clogged drain lines, sewer lines, and small culverts. Using high pressure water through a speacially designed hose and a Jetter nozzle, you can blast through heavy clogs. Jetter Nozzle This nozzle comes in sizes that range from 1/8” to ½” . They have strategically placed orifices that allow them to act differently in the line being jetted. There are many types of nozzles available including, laser, ram, corner, and rotary. OHV Overhead Valve OHV is an efficient internal combustion engine that runs cooler and helps to reduce emissions. OHVI Overhead Valve Industrial OHVI is an efficient internal combustion engine that runs cooler and helps to reduce emissions. This is a more rugged version of the OHV. Powder Coated Powder coating is painting process that creates a super bond of the paint and the surface by using heat to bake the paint to the surface. Pressure (PSI) PSI is the scientific measure for pressure. PSI stands for pound per square inch. Pressure washers can have a PSI as high as 60,000, however most machines are between 3-4000psi. Pressure Washer Hose This is a wire braided hose that can accommodate pressures up to 5000PSI. Hose may be double braided, or single braided. Grey hose is a non-marking hose; however it may wear out quicker than other hoses. Pressure Gauge This is a device used to measure both working pressure and peak pressure depending on where on your machine it is installed. Pressure gauges are ideal for jobs which require exact pressures. Purge A method of eliminating air from a pressure washer. RPM Rotations Per Minute RPM is how many rotations per minute an engine makes. Most engines in the pressure washer industry run 3450 RPM. Spray Nozzle A spray nozzle is located on the end of your wand and is interchangeable to create different angle fans. As you use different nozzles you will increase or decrease the width of the fan.

Typical Pressure Washing Spray Nozzles

  • 0° Spray Tip – RED - This tip is not recommended for wood applications, itsstream of water is to narrow and concentrated. This tip would be ideal for concrete, and metal.

  • 15° Spray Tip – YELLOW - This tip is a heavy duty cleaning or stripping tip. Youcan use this tip for cleaning concrete, loose paint, and driveways.

  • 25° Spray Tip – GREEN - This tip is for general washing purposes. You will find yourself using this tip for your deck, siding, and your car.

  • 40° Spray Tip – WHITE - This tip has the least amount of impact. The white tip is great for rinsing, cleaning out your gutters, and other sensitive jobs.

Thermal Relief Valve This valve is used to alleviate the over heated water in a pump when the trigger gun is left in the off position with the engine and pump running. As the machine continues to run the water in by-pass mode will heat up causing damage to the pump. The thermal relief valve will release the water allowing cool water to flow into the pump preventing any damage. Trigger Gun This gun is used to control the water flow. Once you pull the trigger you have water let off the water stops. Unloader Valve The unloader valve allows the water to by-pass in the pump head when you have the trigger gun in the closed position. This prevents pressure build up and possible damage to your equipment Wand A device used to extend the water away from the trigger gun. Your spray tips will connect to the end of the wand. Wands come in many lengths and can even be extended up to 24’. Most wands are made of aluminum; however some telescoping wands may be fiberglass.

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