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The Pressure Washer

Probably the easiest way to understand how a pressure washer functions is to diagnose a unit and see how it is constructed. We have selected a cold water portable unit for this purpose.

  1. First you have your power source (engine or motor) this is what created the energy to drive the pump. It and the nozzle are what determines the cleaning effect.
  2. The heart of any pressure washer system is the high pressure pump. They are a positive displacement reciprocating type pump – either plunger or piston version. Plunger is the most common as they are more efficient and have longer life. Plungers are usually made of ceramic which is very hard and less prone to wear. Plunger pump can be described as a plunger that moves back and forth against a stationary seal or packing. Whereas a piston pump is where the packing is attached to the piston rod and moves against a smooth cylinder wall. Piston pumps generally have better priming characteristics but cannot operate at as high a pressure and have shorter life.

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The Role of the Unloader

The trigger gun and unloader valve are the two main components of the most common safety system for high pressure cleaning equipment.

Essentially, depressing the trigger allows water to flow out of the system through the nozzle under pressure while releasing the trigger diverts water flow back to the pump. The pump, however, continues to run.

The gun, with the unloader valve, forms a valve system which gives the operator immediate control of water flow or, in some types of systems, pressure. Water flow can be turned on or off by depressing or leasing the trigger, or in “dump gun” systems, system pressure can be drastically reduced to safe levels.

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Basic Maintenance High Pressure Plunger Pumps

This article is meant to provide an overview of basic maintenance high pressure plunger pumps in industrial applications. The pump is the heart of today’s pressure washer, and it is usually the most neglected component in the system. As long as it is working it is not thought about, as soon as it fails it has the highest priority.


It has been documented that the pump is probably the earliest form of machine dating back to around 2000 BC. Today the pump is the second most common dynamic machine in use. The electric motor claims first place

The reciprocating pump first appeared during Roman times (250-0 BC); it was operated by hand, water animal or wind power.

This article will only touch the tip of the maintenance structure. Each item of a system could be written about in depth. The intention for this article is to hopefully arouse your interest in safeguarding your personnel and equipment by looking at maintenance.

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