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Pressure Pump: The Heart of a Pressure Washer System
Pressure Pumps

A high-pressure pump is like the “heart” of any pressure washer system. Pressure pumps are considered high-pressure when they create an amount of pressure greater than 150 PSI (pounds per square inch). The most popular pressure pump found on power washer systems today is the triplex positive displacement reciprocating plunger/piston pump. With these smooth flowing pumps, the pressure and volume remain the same while the fluid goes through the channels and enters the restrictive orifice on the nozzle. It is the pushing of the fluid through the restrictive nozzle that creates the pressure, not the pump itself.

The best pumps use solid ceramic plungers and come “pre-plumbed” with an unloader (a safety valve that controls the flow of exiting water), garden hose and pressure hose fitting capability, and thermal relief valves. The well known brands, such as Cat, General, Comet, Giant and AR use high quality components and are known for long lasting seals, superior construction, and, in general, continuous duty with minimal maintenance. (Some use forged brass manifolds that are guaranteed for life.)

Industrial pumps have their own set of standards and options to take the abuse and wear of constant heavy work. They often have die-cast bodies, brass heads, cooling fins, over-sized bearings and special valve cages to provide extended life of the pumps.

Pumps can have mounting options for left or right, have vertical or horizontal orientation, be frame mounted, self-priming, multi-stage, corrosion resistant and have adjustable speed options. Exploring the many options available today will take a little time, but it will be worth seeing all your choices before you make an uninformed decision.

Thermal relief valves are important for the life of your pump. A Pressure pump is made to handle water that is about 68°. If the water gets too much hotter, vaporizing can cause air bubbles that can explode when they reach the high-pressure chamber. This can cause what is known as cavitation. It can blow a hole right through the pump! It is never a good idea to leave the pump running in by-pass mode for more than 2-3 minutes without triggering the gun. Triggering will send cool water through the pump and cool down any over-heated water. If this can’t be done, you should turn the pump off while pausing for any length of time.

To pick the proper pressure pump for your power washer, you need to know the size/capacity of the engine. Each power washer engine is designed to deliver a certain amount of cleaning units. Cleaning units (CU) are figured by multiplying the psi (pounds of pressure per square inch), x the gpm (gallons per minute.) A quick calculation is to multiply the engine’s horsepower by 1100. This figure will be the CU’s your engine is capable of delivering.

A pressure pump can be used to transfer (push) water through the power washer, or to create suction. Either way, it displaces a fluid—and knowing what fluid you are working with is important to the life of your pump. Before running any chemicals through your pump, check with the manufacture’s listing to prevent corrosion or other damage to the pump. Stainless steel versions are often made to withstand heavy chemical usage.

With proper use and regular maintenance, your pressure pump should last for years—but if maintenance is required, replacement parts are easily attainable. Some common sense maintenance tips are to change the oil every 3-5 months and check the level each time you use the pump. Always lubricate the pump according to manufacture recommendations. Checking for weak, worn, pressure hoses, and clean nozzles is wise too. Sometimes the pump is thought to be failing when in fact the nozzle head is becoming clogged.

If winterizing machinery is an issue in your area, be sure not to forget your pressure pump. Flush with clean water, flush with anti-freeze, and put it away dry! Don’t ever store your pump away, or even leave it exposed to freezing temperatures, with water left inside.

Problems with your pressure washer may well mean a problem with your pump. But today’s pumps are amazingly well built, and with a bit of care, should withstand all the work you put them through for many years.


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