High pressure cleaners - effective and water-saving

27th of December 2017
High pressure cleaners - effective and water-saving

The public perception of pressure washing is that it is practical as well as time-saving, but it also comes under critical scrutiny. With respect to water consumption, the key issue is sustainability, but there are also the problems associated with treating sensitive surfaces. What is the truth about conventional pressure washing, and what are the alternatives? Kay-Uwe Müller of Kärcher writes for ECJ.

The history of pressure washers is a success story. These versatile machines have long been all-rounders that have become crucial in countless areas, whether with a electric motor or combustion engine, mobile or stationary. Pressure washers are commonly used to clean roads, public squares and buildings. In agriculture they play their part in maintaining vehicles and machinery or cleaning animals stalls, for example. In the motor vehicle industry, they are used for washing engines, underbodies and small parts.

High pressure cleaners are often found in areas where hygiene is particularly important: in swimming pools, medical facilities or in food and beverage industry operations. Virtually no other cleaning technology is quite so flexible in its applications.

In addition to flexibility, the pressure washer has other features in its favour:

• Even stubborn dirt can be removed with the right combination of pressure, water volume, temperature and detergent
• The high pressure jet reaches areas that are difficult to access, and adapts to irregular surfaces
• Dirt and germs are not spread because cleaning is done without contact.
• Mechanical cleaning is an environmentally-friendly alternative to chemical cleaning, and in many cases yields a better result in a considerably shorter time.

In practice, both cold and hot water pressure washing are used. A lot of dirt can reliably be removed with cold water. Accessories such as brushes and scrubbers that are connected directly to the pressure washer lance reinforce the mechanical cleaning effect. Detergents can also accelerate the process, or improve results. Most cold water appliances can be also operated with hot inlet water up to 60°C, which increases the cleaning effect. Hot water offers advantages when removing oil, fats and proteins – particularly when they are already encrusted.

However there are some questions, particularly concerning the water consumption of high performance appliances, and preventing damage to unsuitable surfaces. What are the answers to these questions?

The constructional design of the nozzle has a big impact on ensuring cleaning is as fast and thorough as possible. Even minimal changes to the geometry have huge effects on the impact pressure. This is what lifts and loosens the layer of dirt. The influencing factors of nozzle pressure, water volume and jet geometry fundamentally depend on the shape and size of the nozzle profile.

Important to know: the impact pressure falls considerably the further you are from the object. At a distance of 30 cm, the impact is only around one hundredth of its initial value. For effective cleaning with optimum results, the distance from the nozzle to the object should therefore be no greater than 10 to 30 cm.

Pressure washers save water

In addition to the nozzle geometry, the main deciding factors are pressure and the pump output capacity. Many users look in particular at the maximum pressure and related dirt-busting effect. In many instances however, the volume of water and its washing performance is of greater significance to the cleaning result. This is particularly important where – in the construction industry and agriculture for example – a lot of dirt needs to be removed from machines and floors.

A high cleaning effect also requires high water flow volume. High performance machines operate at around 1,000 litres per hour. That sounds high but is low in comparison with a standard water hose where the flow rate is up to 3,500  litres per hour. This means pressure washing uses water very efficiently. As well as meeting demand for sustainable solutions in countries such as South America or Australia, where during dry periods there are stringent conditions placed on the use of pressure washers in order to save water. There are even greater savings due to the fact that the high water pressure means the job can be completed more quickly.

Ecologically good - many machines can also be operated with recycled or conditioned water. This practice is particularly effective when used at gantry car washes, for example. Water recycling systems can be installed here, saving up to 98 per cent of fresh water – for a comparatively low investment.

Accessories for better results

With many cleaning tasks, the use of accessories can improve results, reduce the time required, and make the work easier and more ergonomic. Accessories such as brushes and scrubbers that are connected directly to the pressure washer lance reinforce the mechanical cleaning effect. A further accessory that is increasingly used is the patio cleaner. The rotating nozzle bar facilitates fast and even operation over large surfaces. The cover serves simultaneously as a spray guard. It prevents dirty water from escaping, and eliminates the need to rinse and dry walls and fixtures after cleaning.

Models with integrated extraction based on the Venturi principle offer an added benefit. It not only leaves the floor clean, it also dries more quickly. In practice, this avoids time and effort wiping the area down again.

For many tasks, reduced operating pressure is perfectly sufficient. Machines where reduced pressure can be used support the efficient use of water. This also allows the machine to respond flexibly to different hardnesses. The control is either on the machine, or conveniently positioned on the gun itself.

Ergonomics also play an important part when considering efficiency and sustainability. The gun should sit comfortably in the hand and require little effort to pull out or hold it. It is particularly user friendly when the pressure and water volume can be adjusted on the handle itself. An angled, rotatable jet pipe means even corners and other hard-to-access areas can be reached. The curved design offsets the recoil to some extent, and ensures that the lance is easy to hold in high pressure operation. The jet pipe and nozzle can be easily changed without the need for tools, saving time.

Hot water pays off

There are numerous features in favour of using cold water pressure washers. The universal machines are generally compact, easy to handle and easy to transport if they are frequently used in different areas. Hot water pressure washers offer even more advantages. Heat energy is a key factor in sustainably influencing and accelerating cleaning processes. Increasing the temperature results in:

• The same cleaning result with a lower impact pressure
• Improved cleaning results with the same impact pressure.

The engines on modern hot water pressure cleaners can be operated using standard biodiesel. Machines with an electrically hot water boiler are used where exhaust gases need to be avoided – for example in industrial kitchens, swimming pools or other enclosed spaces.

Stubborn dirt can be tackled more quickly and effectively with hot water machines. The combination of hot water and high pressure increases efficiency in particular. In practice, using hot water reduces the operating time by around 35 per cent – usually coupled with significantly better results.

Whereas cold water machines usually yield acceptable results only in combination with additional detergents, temperature is a factor here. Using less or no detergent benefits the environment. Introducing heat means residues of dirt and grease are broken down and loosened more quickly.

Oils, fats or encrusted deposits of soot melt away with the introduction of heat, and are easier to remove more thoroughly. A major advantage of using hot water pressure washers is the faster drying time. Surfaces cleaned with hot rather than cold water warm up easily, and so generally dry more quickly, and are ready for use in a shorter time.

Hot water pressure washers play an important part in reducing microorganisms and germs in hygienically sensitive areas. In the steam mode, machines yield water vapour up to a temperature of 155°C. This effectively reduces harmful germs even before subsequent disinfection. Applications are in the food industry, in industrial kitchens, medical facilities, indoor swimming pools and also in agriculture.

Caring for sensitive surfaces

Hot water pressure cleaners are also able to tackle demanding cleaning tasks. The steam setting is perfect for sensitive surfaces where full cleaning performance is achieved with a considerably lower operating pressure and less water. This means materials that react sensitively to too much water can be cleaned gently, including sandstone façade elements, mineral plaster and other porous natural materials. Even stubborn dirt and deposits can be loosened in an environmentally-friendly way with this process, including layers of bitumen, paint residues, remains of rust, lichen and algae.

Heated are particularly efficient

The biggest advantage of hot water pressure cleaners is the improved cost-effectiveness. They particularly come into their own when used in regular industrial applications - the more intensively the machine is used, the more apparent the cost savings. The higher purchase price is amortised by the lower labour and operating costs. Energy heating costs are soon offset by the significant reduction in water and detergent usage.

Pressure washing continues to be a cost effective and water-saving alternative to manual cleaning using brushes, scrubbers and a water hose. In industrial and commercial use, hot water models offer added benefits, particularly due to shorter working times, their gentle treatment of surfaces, their ability to loosen and remove residues of oil, fat and protein, and to reduce the transmission of germs.


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