Effective and environmentally friendly: Weed removal with hot water

Dealing with weed in an effective manner is a constant challenge in municipalities and agriculture. There are chemical products for this purpose, but these are often environmentally harmful and their use in public spaces is limited. With hot water, dandelions, thistles and more can be removed without using herbicides. A gentle method without harming the environment or surfaces. 

Mann entfernt Unkraut in einem Park mit Heißwasser-Hochdruckreiniger von Kärcher

Reasons for weed removal

Unlike cultivated and ornamental plants, weeds are plants that grow naturally without any human intervention. There are lots of good reasons to remove weeds. In farming, you remove weeds to protect crops. In towns and cities, to keep public spaces clean and tidy and to prevent damage to roads, open spaces and buildings.

Many weeds can spread extremely quickly and/or cause severe damage with their roots. They also have a negative impact on the desired aesthetics. 

 

Weed between paving stones

Treatment methods at a glance

Thermal, mechanical and chemical methods can be used to destroy weeds. They differ, inter alia, in terms of their environmental impact, sustainability and efficiency. An overview of the treatment methods:

 

Type of procedure

Hot water machines

thermal

Hot foam machines

thermal

Hot steam machines

thermal

Hot air machines

thermal

Flame devices

thermal

Weed brush

mechanical

Spray method

chemical


Properties

Hot water machines

Up to 98°C

Kill the parts of plants above ground and the roots below with hot water.

Hot foam machines

> 100°C

Steam machine with additional foam output. The foam is used for insulation purposes and is intended to prevent the steam from cooling too quickly.

Hot steam machines

> 100°C

Kill the parts of plants above ground. However, heat transfer from steam is not as effective as that from hot water. Roots are not effectively attacked.

Hot air machines

> 350°C

Kill weeds with intense heat from hot air.

Flame devices

> 400°C

The plants are heated by burning gas, causing them to die and in some cases burn.

Weed brush

Weed brushes and strimmers remove the plants from the roots.

Spray method

Herbicide is applied to the leaves using a spray unit.


Environmental impact

Hot water machines

low

Hot foam machines

moderate

Hot steam machines

low

Hot air machines

moderate

Flame devices

high

Weed brush

low

Spray method

very high


Effect

Hot water machines

Plants and roots are weakened and destroyed, including the seeds.

Hot foam machines

Plants are weakened and destroyed. Limited penetration.

Hot steam machines

Plants are weakened and destroyed. Limited penetration.

Hot air machines

Surface growth is destroyed. Limited penetration.

Flame devices

Surface growth is burned. Limited penetration.

Weed brush

The parts of plants above ground are removed using a steel brush.

Spray method

Herbicide weakens and destroys the cell structure of the plant down to the roots.


Noise exposure for users

Hot water machines

low

Hot foam machines

low

Hot steam machines

moderate

Hot air machines

moderate

Flame devices

high

Weed brush

moderate

Spray method

low


Special features

Hot water machines

Can be used on all surfaces, including critical and hard-to-reach areas.

Hot foam machines

Can be used on all surfaces, including critical and hard-to-reach areas.

Hot steam machines

Can be used on all surfaces, including critical and hard-to-reach areas.

Hot air machines

Ineffective in moist conditions.

Flame devices

Cannot be used in extremely dry conditions, ineffective in moist conditions.

Weed brush

Standard in public areas; achieves desired clean, smart look in towns and cities as the weeds are removed directly.

Spray method

Generally prohibited, may be used on paved and compacted areas only with special authorisation, certificate of expertise required.


Sustainability / effectiveness

Hot water machines

high

Hot foam machines

high

Hot steam machines

moderate

Hot air machines

low

Flame devices

low

Weed brush

moderate

Spray method

high


Application frequency

Hot water machines

Up to 4 applications in the first year, decreasing the following year.

Hot foam machines

Up to 4 applications in the first year, decreasing the following year.

Hot steam machines

4–6 applications.

Hot air machines

Application must be repeated about every 4 weeks.

Flame devices

Application must be repeated about every 4 weeks.

Weed brush

Application must be repeated about every 4 weeks.

Spray method

Up to 4 applications in the first year.


Overall assessment

Hot water machines

*****

Hot foam machines

**

Hot steam machines

***

Hot air machines

**

Flame devices

**

Weed brush

***

Spray method

**


Weed removal with a Kärcher hot water high-pressure cleaner

Weed removal with hot water

The overview of the treatment methods shows that weeds can be effectively removed using various thermal methods. The principle of thermal weed control is based on a fundamental biochemical rule: most proteins denature from a temperature of roughly 42°C. This means that the proteins change, break up and can no longer fulfil their functions. 

The necessary heat can be generated and applied in a number of ways: directly as a flame or indirectly via thermal radiation, as hot water or steam. Hot water is the only chemical-free method that also reaches the roots. Even if the roots are not completely destroyed straightaway, the weed is further weakened with each hot water application. If you apply hot water regularly from the beginning, regrowth is hampered and the required application frequency will decrease considerably even in the second year. As a rule of thumb, three to four treatments are sufficient in a year.

Tip: Apply at the right time

The best time to remove weeds is in the afternoon. The amount of water stored by plants varies depending on the time of day. It is also best to start with the first hot water application shortly after the weeds have sprouted in spring. As plants get older, they become more resistant to hot water.

Use of hot water high-pressure cleaners

The temperature is decisive when removing weeds with hot water: The hotter the water, the more efficiently the plants can be destroyed. Hot water high-pressure cleaners can provide water at consistently high temperatures of up to 98°C, which is just below the steam threshold and therefore ideal.

The weed removers WR 10, WR 20, WR 50 and WR 100 are suitable as accessories. They vary in their working width and area performance – for a demand-oriented use depending on the area size.

Kärcher weed remover WR 10 for destroying weed with hot water

Weed remover WR 10 with 10 cm spray head and nozzle adapter. For an efficient weed removal also in confined spaces.

Kärcher weed remover WR 20 for destroying weed with hot water

Weed remover WR 20 with a 20 cm wide nozzle bar and integrated nozzle adapter.

Kärcher weed remover WR 50 for destroying weed with hot water

Weed remover WR 50 with a 50 cm wide nozzle bar, adaptive chassis and nozzle adapter.

Kärcher weed remover WR 100 for destroying weed with hot water

Weed remover WR 100 with chassis, 100 cm wide nozzle bar and integrated nozzle adapter. Ideal for large areas.

Tip: Distance between nozzle bar and surface

The optimal distance between the nozzle bar of the Kärcher weed remover and the surface is between 5 and 15 centimetres. You can work comfortably within this range without the weed remover touching the ground. It also means that the loss of water temperature as the water travels to the surface is minimal.

Weed removal with hot water high-pressure cleaner

Topic special "Weed removal with hot water"

In our topic special you will find further information and an overview of the products for weed removal.

Learn more

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