How a pressure washer works?

To understand how to properly use and care for a pressure washer, you need to have at least a basic understanding of how this device works.

The high-pressure pump is the crucial component and "heart" of a washer. It contains plungers, which are small pistons responsible for pumping liquid under high pressure. These plungers rapidly move back and forth with minimal gaps in the pump housing. Therefore, the pressure washer pump is highly sensitive to water quality and cannot handle contaminated liquids. Different pump classes have varying materials for the housing, with fiberglass being common in lower-class pumps, aluminum alloy in mid-range pumps, and brass in higher-class pumps.

A cross-sectional view of a high-pressure washer pump.

The pump of a high-pressure washer is typically powered by an electric motor, although some models may have gasoline internal combustion engines. Electric motors generally require no maintenance, but prolonged continuous operation can cause them to overheat. Low-cost and compact pressure washers usually have operating instructions specifying a maximum continuous operation time of 15 minutes, followed by a 10-15 minute rest to cool down. Mid-range washers can operate continuously for 30 minutes, while advanced models can run for an hour or longer. Brushless motors, found in some washers, are less prone to overheating and offer additional advantages. To prevent motor overheating, many devices are equipped with protective automation, making them more durable.

Popular pressure washers

The remaining parts of the washer are the body (usually made of impact-resistant plastic or fiberglass), a high-pressure hose for supplying water to the gun, the gun itself with a jet tube and attachments (or replaceable nozzles) for spraying water.

The maintenance of the high-pressure washer mainly revolves around taking care of its components and assemblies. While some devices have additional features like detergent and water tanks, transport wheels and hose reels, these details generally do not require special attention.

Portable pressure washer with a set of accessories and supplies.

Water quality for washer

While water from a city water supply or an autonomous water supply systemis generally considered clean, it may not always be ideal. It can contain sand grains, sediment from pipeline walls, or rust particles, which can cause blockages or damage to the high-pressure pump if they enter it. To prevent this, most washers are equipped with a small mesh filter. The filter element is either inserted into the inlet pipe or attached to it from above, and some filters have a transparent plastic housing for easy monitoring and cleaning. To remove sand grains and dirt particles that hinder the liquid flow, simply rinse the filter under running water or use an air compressor if available.

Pressure washers with intake system

It is absolutely not necessary to use a high-pressure device without a filter installed at the inlet (especially if you use a washer with water intake from a container, at the bottom of which there may be dirt and sediment). If you have broken or lost the filter element, then you should buy a new filter. Its price is cheap (compared to the cost of a pump or a pressure washer in general).

The pressure washer filter is washed very simply:

What is the recommended water pressure for the inlet?

To ensure the pressure washer pump can handle the specified water volume in its technical specs, it's crucial to use the appropriate hose for the water supply. Low to medium flow machines typically use 1/2" garden hoses, while high-capacity models require larger 3/4" hoses that can handle more fluid per unit of time. The hose also acts as a damper, smoothing out fluctuations in water pressure within the pressure system, so its length should be adequate (at least 10 or 15 meters). When drawing water from a tank, it's best to use a short hose (no more than 2 — 3 meters) to avoid excessive strain on the motor and pump, which could occur when sucking water through a long pipe.

Insufficient pressure in the pressure line, such as a pinched hose or a partially open valve on the tap, can cause the pump to intermittently stop. However, excessive pressure in the pressure line is also detrimental. Most mini-sinks have a recommended maximum water pressure of 10 bar (although it's important to refer to the specific technical documentation for your device, as it may vary). Therefore, they can be connected directly to a centralized water supply, where the pressure typically does not exceed 6 bar. However, if your water supply system is served by a a powerful pumping station with a pressure of 10 — 12 bar, it is advisable to use a water pressure reducer when connecting the sink to prevent damage.

Many manufacturers also recommend connecting the hose to the faucet not directly, but through a check valve. Its task is not to let the flow of water from the washer back into the water supply system (this happens when the motor is turned on and off), so as not to spoil the drinking water and protect the pipeline from small “water hammers”.

In some countries, the use of a check valve when connecting the pressure washer to the drinking water supply is mandatory.

How does the air entering inside affect the pressure washer pump?

Pressure washer pumps are highly sensitive to "dry running," meaning they should never operate without water for more than 30 — 60 seconds. The pumped liquid serves to cool the rubbing and rotating parts of the high-pressure pump. Extended dry running can lead to overheating and cause the seals and cuffs in the pump to melt. To prevent this, it is essential to connect the device to the faucet using a hose with reliable and strong connectors that won't come off accidentally. Alternatively, clamps can be used, though they may be less convenient. When drawing water from a barrel, ensure the end of the hose is submerged at the bottom of the tank to avoid air intake, and fill it with water before starting the device.

Even a small amount of air entering the pump adversely affects the operation of the pressure washer. Bubbles or "air pockets" in the water line will cause the pump to not work at full capacity and will not produce as much pressure as indicated in its nameplate specs.

When taking water from a tank, it is better to use a short hose to reduce the load on the pressure washer and “load” its end at the bottom.

Hot water and pressure washer: pros and cons

As everyone who has washed dishes or taken a shower at least once in their life knows, hot water washes any dirt better than cold water. Therefore, many owners of pressure washers are tempted to use pre-heated water in order to better and easier wash dirt from the car body, rims, floor tiles, concrete paths or other surfaces. But it is not always possible to do this.

High-pressure washers with 3 in 1 nozzle

Pressure washer pumps tolerate hot water in different ways (those that have bodies made of composite materials are worse, while aluminum and brass ones are better). Therefore, for most high-pressure cleaners, the operating instructions indicate the permissible water temperature (in our catalog of mini-washers, this characteristic is affixed to all models where manufacturers have found it necessary to indicate this parameter). In general, the recommended maximum temperature is around 40°C, although a few models can handle water preheated to 50°C or 60°C. It is crucial not to exceed the recommended temperature, as pumping excessively hot water can lead to rapid pump failure due to overheating.

The ability to operate with heated water is more common among "advanced" washers and professional-grade equipment.

Why and how to drain water from a pressure washer?

After each use, it is recommended to completely, to the last drop, drain all the water from the device. You should do it this way:

  • turn off the engine and disconnect the water supply hose to the device;
  • by pressing the pistol lever, release excess pressure until you hear a characteristic “snort” sound;
  • disconnect the high pressure hose with the gun from the washer;
  • for a short time (no more than 10 — 20 seconds), turn on the motor so that the pump “squeezes out” all the liquid through the outlet that may still be inside the pump and nozzles.

It is especially important to drain the water from the pressure washer after use in cold weather or before putting the device into storage with the onset of cold weather. If this is not done, the liquid in the pump will turn into ice (its volume is 9% more than that of water), which simply literally breaks the pump casing from the inside.

And something else

In order for the pressure washer to function properly and work for a long time without complaints, it is necessary to adhere to a few more simple rules.

  • Modern high-pressure washers are sensitive to power supply quality. Fluctuations or an unstable voltage of 230V can hinder the engine and pump from operating at full power, leading to occasional freezing or pulsating pressure. To address this issue, it is recommended to connect the washer to a power line protected by a voltage stabilizer.
  • Nozzles tend to clog. You should regularly clean the nozzles with a special needle, which is almost always included in the package of a high-pressure washer.
  • It is advisable to use original accessories or at least accessories approved by the washer manufacturer. In our catalog of accessories for high-pressure washers, you can find nozzles and parts for a specific brand and even a specific model.
  • After using car shampoo, detergent, active foam or other automotive or household chemicals with a high alkali content, it is crucial to flush the pressure washer with clean cold water. This step ensures that hoses, tubes, nozzles, the chemical tank and the foam gun tank are thoroughly cleaned from any remaining aggressive substances.
Detergent chemistry is highly effective in removing dirt, but it can be corrosive to the parts of a pressure washer. Therefore, it is necessary to thoroughly rinse the device with clean water after using car shampoos or active foam.

Instead of an afterword

Before purchasing a pressure washer for car and household use, it is recommended to read articles about high-pressure washers to understand their pricing. For beginners, the articles "How to choose a pressure washer" and "Frequently asked questions about pressure washers" are particularly informative and helpful.