Proper cleaning of milking equipment contributes to ensuring that high-quality milk is produced on the dairy farm. Goals of cleaning milking equipment are to prevent microbial growth and remove residual milk solids. Residual milk solids are called “soils” and contain both organic and inorganic materials. Soils that are retained on the inner surface of the milking system provide nutrients and areas for bacteria to grow, and these soils also reduce the effectiveness of the cleaning and sanitizing compounds.

Heguy jennifer
Dairy Farm Adviser / University of California Cooperative Extension – Stanislaus County

The milking system includes the milking claws and inflations, receivers, pipelines and milk storage tank – everything that comes into contact with milk.


Washing the milking equipment requires that you monitor time, temperature, pH and agitation.

Ensure that liquids are flowing through all of the milking machines, that hoses remain in place and that agitation is occurring in the pipelines (evidenced by water flowing into the receiver).

In this article, we’ll discuss how to monitor the cleaning of your milking system by using a watch, thermometer, pH paper and a watchful eye that pays attention to detail.


To clean the milking equipment associated with the milking claws and inflations, receivers and supply lines, the major steps are to rinse, wash, post-rinse and sanitize.

The parameters (time, temperature and pH) will vary slightly for each facility, but the basic principles are the same for all washing systems.


Ideally, pre-rinse all surfaces immediately after milking with lukewarm (100ºF to 110ºF) water to remove milk solids. Lukewarm water should be used when adequate hot water supply allows for both a warm water pre-rinse and hot water wash.

The initial rinse water contains residual milk ( Figure 1 ). When done properly, this rinse removes more than 70 percent of the soil load.

Do not re-circulate this water through the milking system. Discharge the rinse water and continue the rinse cycle until the water appears clear ( Figure 2 ).

With your thermometer, monitor the temperature of the rinse cycle at the return line:

• Rinse water temperature below 93ºF will allow milk fat to deposit on milking equipment surfaces.

• Rinse water temperature above 120ºF will denature any remaining protein and create protein films. These films are colorless at first but develop a yellow color as they build up. Protein films provide contact areas on surfaces where bacteria can grow.

Drain all rinse water before beginning the next step.


To prevent premature cooling of the wash solution, turn off the vacuum pump while refilling the system with hot water and detergent.

Most dairy farms use a chlorinated alkaline detergent in either liquid or powdered form. Add your detergent to the wash water according to manufacturer specifications.

Why an alkaline detergent? Lipids (oil and milk fat) and water do not mix.

The (basic) pH of the detergent breaks up any remaining milk fat into tiny droplets, suspending the fat in the detergent wash water. Use your pH paper to check that the pH is between 11 and 13 ( Figure 3 ).

Why chlorinated? The chlorine increases the solubility of any remaining protein and helps to remove it with the detergent wash water during the wash cycle.

The temperature of the chlorinated alkaline detergent solution should be between 160ºF and 170ºF ( Figure 5 ) at the start of the wash cycle – check this with your thermometer. Typically, the wash cycle is at least 10 minutes, but this will vary with each parlor depending on size and type of parlor.


It is important the temperature of the chlorinated alkaline detergent wash does not fall below 120ºF ( Figure 6a ) as it leaves the system (check this with your thermometer), because any milk solids either in solution or in suspension may be re-deposited on contact surfaces.

The temperature of the wash water should be measured for each wash cycle. Use your watch to time the wash cycle and your thermometer to measure the temperature of the wash water at the sink.

Temperature and time should be monitored during different seasons of the year – the different seasons (summer versus winter) can have an impact on time and temperature conditions for your wash system.

In all cases, hot water volumes need to be sufficient to allow wash cycles to run at least 10 minutes above 120°F. If this standard can’t be met, hot water storage volumes must be increased.

Drain all chlorinated alkaline detergent wash solution before beginning the next step.

Post-rinse or acid rinse
Rinse the milking system with lukewarm (100ºF to 110ºF) acidified water for 3 to 5 minutes. Use your pH paper to check that the pH is between 3 and 4 ( Figure 6b ).


The acid rinse prevents any milk minerals from accumulating on surfaces.

When minerals collect with organic material on equipment surfaces, milkstone (a white, chalky film) develops. Milkstone provides areas on contact surfaces for bacterial growth within the milking system.

The acid rinse reduces the pH of the equipment, which helps to prevent bacterial growth between milkings. The acid rinse also neutralizes the chlorine and alkaline residues from the wash cycle and helps to prolong the life of any rubber parts.

State and federal regulations require that milking equipment be sanitized just prior to milking. Most dairies use a chlorine-based sanitizer in lukewarm water (100ºF to 110ºF) for about a 5-minute cycle.

This step can significantly reduce bacteria counts, particularly if there is more than one hour between milkings.

General comments
Be sure the air injector is operating properly throughout all four steps. The air injector admits atmospheric air into the milking system and creates turbulence in the liquid flow to provide a scrubbing action.

Remember that you must wash or rinse the entire surface of the milking system.

The turbulent flow of liquid created by the air injector ensures that the liquid comes in contact with all surfaces inside the pipeline, as well as having the wash liquids hitting the receiver with enough force to wash the inside top and gasket of the milk receiver or milk vats.


An important safety consideration is to never mix acid and chlorinated compounds together, because this mixture will release a hazardous gas that can cause lung damage and even death when inhaled.

All materials used to clean and sanitize milking equipment can cause serious injury if splashed into the eyes or onto the skin.

Always wear protective equipment and exercise extreme caution while working with these materials ( Figure 4 ).

It is important to safety train employees to prevent accidents and ensure safety protocols are being followed after the initial training.

Rinse, wash, post-rinse and sanitize the milking system properly to aid in producing high-quality milk on your farm. PD

References omitted due to space but are available upon request to

Ed DePeters is from the Department of Animal Science, University of California at Davis; Jennifer Heguy is from the University of California Cooperative Extension, Stanislaus & San Joaquin Counties; and Larry Collar is from California Dairies, Inc.

TOP RIGHT FIGURE 1: Residual milk rinsed from pipelines.

MIDDLE TOP RIGHT FIGURE 2: Clear water rinsed from pipelines.

MIDDLE RIGHT FIGURE 3: Check that the pH of the detergent solution is between 11 and 13.

MIDDLE RIGHT FIGURE 5: Check that the initial temperature of the chlorinated alkaline detergent solution is between 160 and 170°F.

MIDDLE RIGHT FIGURE 6A: Check that the return solution does not drop below 120°F.

MIDDLE BOTTOM RIGHT FIGURE 6B: Check that the pH of the acid rinse is between 3 and 4.

BOTTOM RIGHT FIGURE 4: Remember to use safety equipment (gloves and goggles) to protect from splashing.


Ed DePeters
Department of Animal Science
University of California – Davis