DISEASE PREVENTION – Is pressure washing enough?

Disease Prevention is essential on farms

When it comes to disease prevention cleaning is essential in a farming environment, especially at the end of milking, or when machinery is dirty. Using pressure washers is a standard procedure, but new findings have come to light on whether hot water or cleaning agents and disinfectants should be used.

Disease prevention on the farm is essential

The Thuringian State Office for Agriculture, Germany carried out cleaning tests to compare the use of hot and cold water in disease prevention. The research goal was to test the cleaning effect and above all the pathogen eradication effect achieved by pressure washers with improved technical features that eject water at temperatures of 80°C and more, at different water flow rates, working pressures, and exposure times. All tests were conducted without the addition of cleaning agents and disinfectants. Swabs were tested after breeding for staphylococci, streptococci, gram-positive farm bacteria, spore formers, and coli bacteria. Detailed tests were undertaken on the effect of using hot-water machines for cleaning and disease prevention:

  • Animal transport vehicles
  • Heavily soiled manure spreaders
  • Calf huts
  • The stalls of a pig-breeding plant

The analysis of cleaning results shown in Table 1 shows how the cleaning and pathogen reduction goals were achieved. This is particularly clear in the image documentation. In the case of the heavily soiled manure spreader, the visual impression of cold-water cleaning compared with hot-water cleaning was especially convincing.

Disease Prevention Testing - Comparison of vehicle cleaning with cold and hot water

If pathogen reduction is not a priority, cleaning with warm water at approximately 60°C is adequate. The cleaning of calf huts places more stringent demands as regards the pathogen status of the huts after cleaning. When the next calf is placed in the hut it should not be confronted with bacteria from the previous inhabitant. Prolonged periods of vacancy make additional interim disinfection necessary.

Disease Prevention Testing - Comparison of hut cleaning efficiency

For the purpose of testing, huts were cleaned with cold water, warm water at 60°C, hot water at 80°C, and in each case swabs were taken after drying. There were clear differences in ineffectiveness. Cleaning with water at 60°C did not eradicate or minimise some types of pathogens. Cleaning with hot water at 80°C and with steam produced a very good effect. The huts and the floor were almost bacteria-free.

Thorough and time-efficient cleaning and disinfection in all areas of agricultural production can only be achieved by using hot-water pressure washers. Cold-water models can achieve a certain basic degree of cleaning by means of high pressure and a large amount of water. As soon as higher levels of fat removal or, indeed, bacteria reduction are required, they are largely ineffective, however. Using chemical cleaning agents to assist in the cleaning process with cold water is inappropriate.

The test series showed that hot-water pressure washers can achieve a drastic reduction in bacteria levels even without using cleaning agents and disinfectant solutions. In many cases, disinfectant usage can be reduced or the disinfection cycle protracted. This saving and the reduction in working time required usually more than offset the cost of using hot water.

Buildings and equipment are also less subjected to chemical contamination. The risk of residues in agricultural products and the environment is minimised. Compliance with statutory requirements such as for disinfection of animal transporters is, of course, essential, and operatives must work precisely as a precondition for success in cleaning and bacteria reduction.

Given the low impact pressure and energy density of steam, cleaning with the full amount of water, the highest possible pressure and at 80°C, is usually to be preferred. A minimum hot-water pressure washer requirement is a water throughput of 1,000 l/h and a jet pressure of 180 bar. Less will not ensure reliable results.


  • Cold-water pressure washers have a lesser cleaning effect than cleaning with hot water.
  • If hot water at a temperature of 80°C is used for cleaning, a second operation using disinfectants can usually be dispensed with.
  • Savings of time and resources financially offset the energy required to generate hot water.

Test equipment used: Cleaning with hot water at 60°C Karcher HD 13/18-4 SX Plus: 630 to 1,300l/h water flow rate, 30 to 180 bars of pressure, maximum water intake temperature 60°C Hot-water and steam cleaning Karcher HDS 13/20-4 S: 650 to 1,300 l/h water flow rate, 30 to 200 bars pressure, maximum temperature 80°C at a maximum water flow rate and pressure, 155°C at lowest.