Direct drive Power WasherTo get the most out of your power washer it's important to understand it's major components and how they fit together to create a power washer system that works. For an example, let's analyze the most common machine sold in the market today. The portable direct-drive power washer cold water unit.
POWER SOURCE
The power source can either be a gas powered 4 stroke small engine or an electric motor. These are coupled directly to the pressure pump via a mounting flange. Shaft sizes are usually 3/4", 1" and 1-1/8" diameters there are others but these are the most commonly used.
Gas engines typically operate at 3600 RPM with no load and 3450 RPM when directly coupled to a high pressure pump.
Electric motors are the most compact but are lesser in cleaning power when limited to a 115V power source. These are generally lower in cost and are mostly sold for residential and semi-professional usage
Gas engines are ideal for outdoor use when fumes and noise are not issues. Because they do not require a power cord they are more portable too. So we'll use a gas power source in this example.
THE INLET WATER SUPPLY The inlet water supply should produce at least 1 gallon more per minute water flow than your pressure pump requires. If this checks out then water filtration is the next consideration. At the very least the fitting to attach the garden hose should contain a wire mesh screen to filter sediment or other solids in the water flow prior to entering the pump. There are several different types of inlet filters available, the best incorporates a clear bowl which allows for quick and easy visual inspection prior to each use. Don't "gloss" over this point because something as seemingly insignificant as a grain of sand can score plungers and damage seals if allowed to enter the pump.
THE HIGH PRESSURE PUMP You've now arrived at the "core" of the system, the high pressure pump. All are positive displacement reciprocating pumps either piston or plunger types. Plunger pumps are the most efficient and have a longer life, therefore they are the most commonly employed pumps found on a quality power washer today. There are duplex and triplex plunger pumps. Plungers are typically made of ceramic, a very hard material with excellent wear resistant charachteristics. The triplex pump has become the most popular due to the smoother flow it creates. These pumps are incredibly robust and virtually trouble free when properly maintained. Most people suspect the pump first when experiencing a problem but amazingly 90% of problems can be traced to causes other than the pump.
THE UNLOADER VALVE This is the main "safety" in your power washer system. The most commonly used is the "pressure actuated" type valve. When the pressure gun trigger is released the valve senses the pressure build up and like a "traffic cop" it diverts the water flow from the pump outlet back into the inlet side of the pump this is called "bypass mode." Without this critical component this closed-gun situation would build pressure to the point where it would stall the power source, rupture the gun, hose or even the pump itself.
HIGH PRESSURE HOSE A high pressure hose is composed of an inner tube in which the water flows. This is wrapped in either a single or a double braid of wire mesh. This is in turn surrounded by a rubber outer cover. The cheaper hoses are covered in a thermoplastic material the better hoses have rubber covers. Most hoses are manufactured with burst ratings 4X their rated working pressure. When matching hoses to machines try to use a hose rated slightly higher than the psi rating of your machine. It will last longer. Typical psi ratings are 3000psi, 4000 psi ,4500 psi, 5000psi and 6,000 psi. 3,000 and 4.000 psi hoses are generally single braid while 5,000 psi and above are virtually always double braided (2-wire).
TRIGGER GUNS Trigger guns that stop the water flow are the most commonly used guns in power washer systems equipped with unloader valves. Front entry guns are common on the lesser priced units and rear entry guns are far and away the most popular. Rear entry guns do a better job of keeping the hose out of the operators' way and are better balanced.These guns control the water flow via a spring, ball and seat which are actuated by the trigger. When the trigger is released the ball is pressed against the seat by the spring and water, aided by a check valve in the outlet of the unloader. Water is "trapped" in the hose under pressure and the pump enters bypass mode. With this setup you will experience some "kickback" when you squeeze the trigger so be careful when using ladders and other types of access equipment.
HIGH PRESSURE NOZZLES The high pressure nozzle is a much more important component to the power washer than most realize. This creates the restriction that allows the water flow to become "pressurized" and delivered with such force. A worn nozzle will reduce pressure noticeably. A mismatched orifice can have the same effect. A nozzle with little to no wear and one with an orifice properly sized to your pumps' output will get the most performance from your machine. This completes power washer 101 If you already knew all this that's ok. Future pages will explore each of these components in more depth.
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