Cleaning your milking system


11 min read

The plant cleaning process The four key elements Plant cleaning routines Cleaning procedures Safety when using chemicals Benefits of cleaning systems Machine cleaning requirements Circulation cleaning sytems Reverse flow cleaning systems Bucket washing Bulk milk tank cleaning systems Conclusion

Keeping your milking system clean and safe is an essential part of farm maintenance. The cleanliness of the milking plant and the dairy is critical, so understanding your system and the processes of cleaning is very important. Cleaning must be done properly as bacteria can build up in the plant and contaminate milk. The bacteria affects milk quality by breaking down the components in the milk. This reduces the shelf life of milk and milk products, and produces off flavours in cheeses and milk powders. The New Zealand Food Safety Authority has strict guidelines about dairy plant cleaning procedures to maintain milk quality standards.

The plant cleaning process

Bacteria can enter the plant from cows (teat skin and infected udders) and the environment (drawn into the cluster). The milking environment is ideal for bacterial growth. Effective machine cleaning will control the presence of bacteria in the plant. The quality of the water used is very important in achieving a successful clean.

The four key elements of the cleaning process


Water which is too cool leads to redepositing of the milk residues removed, and water which is too hot denatures protein, breaks down detergents, and damages seals and rubberware.

  • Aim for a temperature of 80-85°C as water exits the hot water storage cylinder.
  • Hot water washes should be dumped when wash water temperature falls to below 55°C.


  • Hot water must contact the surface for at least 4 minutes; this should be extended to 7 minutes by re-circulating during an alkali wash. Pre-heating the plant will help achieve at least 5 minutes of contact time at the recommended temperature.
  • For the milking plant, 10 litres of hot water per cluster is recommended to achieve sufficient contact time.
  • For the bulk milk tank, hot water should be a minimum of 2% of the bulk milk capacity or 120 litres for 5,700 litre tanks or smaller.

Kinetic energy

  • Air injectors and a reservoir of water at the end of the milk line can create a slug formation for cleaning the top of the milk line.
  • Small flushing pulsators used to induce turbulence are largely ineffective and regular brushing or use of a large flushing pulsator/air injector may be required.
  • Milk lines generally require turbulence created via an effective flushing pulsator to fill the line and clean the milk line, or some alternate effective cleaning system.

Chemical energy

    • Acid detergents remove mineral deposits. They can be used in hot or cold water but are more effective in hot water. Acid sanitisers commonly contain chemicals which also kill bacteria. These sanitisers are intended to stay in the plant after washing to provide extended protection. Acid sanitisers should always be added to the final wash.
    • Alkaline detergents remove fat and protein. If left in the plant, they can cause damage to rubberware so they must be followed with an acid wash to neutralise the alkali and leave the plant sanitised. The alkaline detergent is almost always chlorinated, or chlorine added.

Plant cleaning routines

As a minimum the following steps need to be carried out:

  • Cold water rinse after every milking.
  • An acid wash after every milking.
  • An alkali wash at least twice weekly.
  • An acid rinse after every alkali wash.
  • Rinsed and drained. 

Further detail on milk plant and vat cleaning requirements can be found in NZCP1.

Example of an ideal cleaning sequence:

Cold Water Rinse

  • The post milking rinse needs to be completed immediately after milking or milk collection. It rinses most of the residual milk from the milking system and bulk milk tank

Hot Water Alkaline / Acid Wash

  • The milking system should be hot washed as least once a day and twice a day during high risk periods (e.g. when grading, calving). The bulk milk tank should be hot washed after every collection. The purpose of the hot detergent wash is to remove any adhered non-rinsing milk residue. This process should alternate between acid and alkaline in some systematic way to ensure all residues are removed on a routine basis.

Alkaline Detergent Wash

  • A hot water alkaline wash should be carried out at least twice weekly on the milking system and bulk milk tank. The wash water should be recycled for 5-7 minutes once water discharging the plant/tank is hot.

Cold Water Acid Wash

  • The cold water acid wash is normally carried out at night and hot alkaline washes done after the morning milking.

Acid Sanitiser Detergent Wash

  • This should always be the final wash through the milking system and bulk milk tank. Acid sanitiser washes can be used hot or cold.

Typical plant wash programme

Morning Wash
  Mon Tues Wed Thur Fri Sat Sun
Rinse C C C C C C C
Alkaline H       H    
Acid Sanitiser C H H H C H H

Morning wash - C = Cold wash, H= Hot wash

Afternoon Wash
  Mon Tues Wed Thur Fri Sat Sun
Rinse C C C C C C C
Acid Sanitiser H H H H H H H

Afternoon wash - C = Cold wash, H= Hot wash

NB. The alkaline wash should be recycled for 5-7 minutes (if wash water falls to 55°C it should be immediately dumped).

Typical bulk milk tank wash programme

  Mon Tues Wed Thur Fri Sat Sun
Rinse C C C C C C C
Alkaline H       H    
Acid Sanitiser C H H H C H H

Following milk collection wash - C = Cold wash, H= Hot wash

NB. The alkaline wash should be recycled for 5-7 minutes (if wash water falls to 55°C it should be immediately dumped). 

When milk is collected every second day alkaline wash every second pickup.

Documenting cleaning procedures

All farm dairies require a written cleaning procedure that is laminated and displayed prominently in the farm dairy. Even if you are the only person working on the farm, there may be a time when someone needs to unexpectedly cover for you.

The procedures must be written clearly so that someone who has never worked in your dairy before can accurately follow the procedure.

Safety when using chemicals

General actions to take:

  • Scourer gloves are great for cleaning cluster exteriors.
  • Keep a thermometer in the dairy for checking water temperatures. Glass and mercury thermometers are not allowed for measuring temperatures in the dairy (NZFSA, 2007).

Handling chemicals

  • Designated (and marked) chemical measuring jugs save time, and chemicals.
  • Always read labels before using unfamiliar products.
  • Never mix acid and alkaline detergents together.
  • Always add chemical to water, not the other way round.
  • Never mix chlorinated products with acid as this can produce a poisonous gas.
  • Never mix chlorinated products with oil or store them close together - there may be a flammable reaction.
  • Never store chemicals in unmarked containers.
  • Never store non-dairy chemicals such as herbicides and pesticides with dairy chemicals.
  • Never use a food contact hose for filling non-dairy chemical containers.

Mixing jugs.

Protective clothing

Always wear protective clothing when using chemicals including:

  • safety goggles
  • apron or other waterproof clothing
  • waterproof gloves
  • gumboots.

What are the benefits of cleaning systems?

Machine cleaning systems maintain milk quality by aiming to remove ALL milk residues from the plant and destroying any resident bacteria.

The benefits of selecting the right cleaning system and following it successfully include:

  • Maintaining milk quality. Put in place a process to ensure cleaning is done properly, so that all residues are removed and bacteria are destroyed.
  • Ensuring safety issues are considered.
  • Increased milking efficiency: installing a well designed system will ensure efficient operation.
  • Reduced costs: installing the right system will keep operating costs to a minimum.

Automation of the cleaning process can be advantageous as it provides consistency of operation, eliminates human error, and prevents health and safety issues associated with handling strong chemicals and hot water.

If the cleaning process is automated the operator needs to periodically check the automation to ensure the plant is cleaning properly.

Machine cleaning requirements

An easy-to-operate method of cleaning the pit and milking platform is essential. Some larger dairies are installing automatic washing systems on their milking platforms. This is especially useful if the dairy is used for long periods of time.

Features of a cleaning system

A cleaning system should have the following features:

  • Adequately sized and configured wash line.
  • Minimum flow rate of 3 litres per minute per cluster.
  • Flow rate through the first jetter should not greatly exceed the last.
  • A flushing pulsator/air injector may be installed at the end of the milk line to ensure it is cleaned effectively. If the milk line is a loop line then a tap is installed near one of the milk line entries to the receiver with a flushing pulsator/air injector installed before the tap, at the top of the milk line. During washing the tap is closed and the flushing pulsator/air injector turned on.
  • Cause minimal liner stretch and distortion.
  • A high flow, rapid dump hot water service to save time filling drums.
  • Liners compatible with jetters.

Circulation cleaning systems

This type of system is recommended for all dairies.

At the completion of milking, the clusters are connected to ‘jetters’ that are in turn connected to a wash line.

When the milking plant is turned on the vacuum created by the plant draws water from the wash tub through the wash line.

When hot washing, the water should be circulated through the plant for 5-7 minutes, or until it reaches the minimum dump temperature (about 55°C). This is done by connecting a recycle line from the delivery line to the wash tub.

To ensure effective cleaning a minimum water flow of 3 L/min is required through each cluster.

To clean the milk line effectively a flushing pulsator/air injector is normally needed. The flushing pulsator injects air and water into the milk line every 30-45 secs.  This injection of water and air creates a turbulent flow of wash water through the milk line which helps to effectively clean the milk line.

Advantages and disadvantages of circulation cleaning systems
Advantages Disadvantages
Safe to operate - especially if chemical dosing is automated. Care should be taken if re-circulating the washing solution as it may become too cold and re-deposition may occur.
Good contact time and turbulence in cluster. High initial capital cost.
Improved turbulence for large bore milk lines with air injector fitted. Chemical handling/spillage is possible with non automated systems.
Easy to re-circulate wash water to increase contact time and effectiveness of detergents. Monitoring is required to ensure that all clusters get water, every wash.
Easy to automate. Monitoring to ensure jetter rubberware is not stretched or split - air admission.
Advantages and disadvantages of automating circulation cleaning systems
Advantages Disadvantages
Can eliminate manual handling of chemicals and allow the operator to leave the area while the plant is cleaned. Not working correctly and going unnoticed by people until demerti milk occurs.
Provide consistent operation regardless of operator, providing they are well maintained. Detergent dispenser not refilled and run empty.

Reverse flow cleaning systems

Reverse flow systems are no longer recommended by the industry for use in New Zealand dairies apart from to rinse the plant with cold water.

In this system, the vacuum pump is switched off and the hose is connected to the milk line between the receiver and the milk pump.

The wash solution is pumped through the hose in to the milk line and passes out through the clusters, flowing in the opposite direction to the normal milk flow.

They have a higher water requirement than other wash systems.

Advantages and disadvantages of reverse flow cleaning systems
Advantages Disadvantages
Relatively simple to operate. Expensive to establish, with larger hot water requirements and pumps required.
Quick to operate, and no time or energy
required for attaching jetters.
Expensive to run due to high water use and high chemical usage.
Quick draining of all milking machine
Contact wash time very limited.
Difficult to automate.
Difficult to perform heavy duty clean if required.
Because liners are not pulsating, they may not be cleaned properly.
Very inefficient use of hot water.
All parts of plant not washed adequately.
Unless well installed can be dangerous to operators.

Bucket washing

Bucket washing is rarely used now in New Zealand dairies.

In this system the machines are left running and the wash solution is drawn up into the machines via cups from buckets.

The wash solution flows through all of the milk pipes in the same direction as the milk. No special equipment is required except buckets.

This system requires 30 litres of water per cluster per day, and has a high labour component.

Advantages and disadvantages of bucket washing systems
Advantages Disadvantages
Inexpensive to establish. High labour cost (if done properly).
Very effective results if done properly. Danger due to carrying of hot water in buckets.
Difficult to circulate detergent should a heavy duty clean be needed.

Bulk milk tank cleaning systems

Automation of bulk milk tank cleaning can enable the tank to be cleaned immediately after emptying, reducing the risk of milk residues setting on the tank surfaces, and therefore limiting the opportunity for bacterial growth.

Different methods of cleaning the bulk milk tank require varying labour inputs and offer varying scope for automation.

Manual cleaning systems

Manual cleaning involves cleaning of the bulk milk tank using buckets and brushes. It is limited to small lidded tanks as good access to all internal surfaces is needed.


  • Inexpensive to establish.
  • Effective results if done properly.


  • High labout cost (if done properly).
  • Danger due to lifting buckets of hot water and detergent into tank. Protective clothing should be worn when manually washing bulk tanks.
  • Prone to people taking short cuts due to time needed to do the job correctly.
  • Areas of the bulk tank are easily missed - under bridge, agitators and corners.

Manual cleaning in place

Manual CIP involves the fitting of a spray ball or similar device into the top of the bulk milk tank. The spray ball distributes cleaning solutions to all of the internal surfaces. Pump sizes, spray ball design and water volumes need to be matched to provide good cleaning.


  • Can be retro fitted to most bulk tanks.
  • Relatively inexpensive to install.
  • Safer.


  • Spray balls can block, resulting in areas of the tank not being cleaned.
  • Limited contact time of detergents if the water is not recirculated.

Automatic cleaning in place


  • Wash cycles can be tailored to suit size and configuration of tank and local resources.
  • Repeatable and consistent wash cycles.
  • Error and fault reporting.
  • Integrated with cooling systems.
  • Usually supplied with a dedicated hot water service.
  • Minimal handling of chemicals.
  • Required volumes of water and chemicals are reduced by recirculation.
  • Tank can be completely washed immediately after emptying.
  • Little labour input.
  • Safer.


  • Wash times can be excessive (outside milk processor requirements) if the water pressure is low.
  • Spray balls can block, resulting in areas of the tank not being cleaned.
  • Expensive.
  • Often only available as an integral part of the bulk tank.
  • No system is fully automatic - chemical drums and effectiveness of wash program need to be monitored.
  • Automated systems failing and going unnoticed by people.
  • Power cuts may change cleaning cycle times.


  • Check that your machine cleaning routine suits the system.
  • Check the milk dockets and if any bacterial alerts/grades show on the docket then complete a full plant/vat inspection.
  • Perform a monthly check on your machine cleaning system to make sure it is working correctly.
  • Use any spare time while the wash is going through to:
    • Check that all of the clusters have water going through them.
    • Check the wash line injector or flushing pulsator is working (you should be able to see turbulence in the receiving can).
    • Time the recycle time of the alkaline washes on the plant and vat and ensure the washes are being recycled for at least 5mins.
    • Check initial hot water wash temps are 80-85°C in the tub and when recycling the wash solution ensure it is dumped before it reaches 55°C.
    • Check that the chiller in the milk silo is on and working.
    • Hose the dairy and yard areas.
    • Update animal health records and transfer any information from whiteboards etc.
    • Plan the effluent irrigator runs and update records
  • When installing a system consider the costs involved and the labour input required.
  • Beware: bulk milk tank cleaning requires the use of concentrated chemicals and/or large volumes of hot water. Health and safety issues arise from this practice. Many tanks are ‘confined spaces’ and entering them can have fatal consequences from asphyxiation. Always remove the silo door when you enter.
  • Never stand in a confined space where acid and alkaline cleaners mix, like at the bottom of the bulk milk tank.
Last updated: Sep 2023

Related content

Milk cooling


8 min read

Pulsation and vacuum


7 min read



5 min read



7 min read