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Brewers Association

25 September 2019

Draught System Maintenance and Cleaning

Editor’s Note: The following is an excerpt from the Draught Beer Quality Manual, fourth edition, published by Brewers Publications and prepared by the Technical Committee of the Brewers Association. This excerpt originally appeared in the July/August 2019 issue of The New Brewer.

In addition to alcohol and CO2, finished beer contains proteins, carbohydrates, and hundreds of other organic compounds. Yeast and bacteria routinely enter draught systems, where they feed on beer and attach to draught lines. Minerals also precipitate from beer, leaving deposits in lines and fixtures.

Within days of installing a brand new draught system, biofilm deposits begin to build up on the surfaces that come into contact with beer. Without proper cleaning, these deposits soon affect beer flavor and undermine the system’s ability to dispense quality beer.

When undertaken using proper solutions and procedures, line cleaning prevents the buildup of organic material and mineral deposits while eliminating flavor-changing microbes. Thus, a well-designed and diligently executed maintenance plan ensures trouble-free draught system operation and fresh, flavorful beer.

Testing for Cleanliness

The following are a few of the most common ways to test for draught system cleanliness.

Sensory Evaluation

A thorough sensory evaluation by a trained taster can reveal signs of bacterial infection in a draught system. However, bacterial contamination begins long before it can be detected by human senses. Draught system maintenance is designed to prevent bacterial contamination from taking hold. If only sensory evaluations are used for testing, it may be too late by the time bacteria reveal themselves through detectable tastes and aromas.

ATP Testing

ATP testing can be a convenient and portable way to test for cleanliness in the field. The ATP test is a process of rapidly measuring for the presence of actively growing microorganisms through the detection of adenosine triphosphate (ATP) using a luminometer (see Figure 1). While ATP testing can be an indicator of cleanliness, it is unable to differentiate between beer-spoiling organisms and other naturally occurring, less worrisome organic material such as yeast.

Fig. 1 ATP testing equipment can be used to verify line-cleaning effectiveness by sampling rinse water

Color Indicators

Some chemical manufacturers have color-changing chemicals that can provide indicators of a draught system’s cleanliness (see Figure 2). Similar to ATP testing, these methods are only an indicator of cleanliness and are unable to differentiate between beer-spoiling organisms and other naturally occurring, less worrisome organic material.

Fig. 2 Color indicators can be used to test draught system cleanliness. Thonhauser’s DESANA™ MAX system changes color, from green to purple, to indicate cleanliness


Taking samples, plating on media, and growing microbial colonies is the only way to truly identify specific microorganisms that are growing in a draught system (see Figure 3). Plating and interpreting samples can identify each type of microbial species and how prevalent it is. Unfortunately, this process is cumbersome in the field, time consuming, and costly.

Fig. 3 Traditional plating techniques can be used to check for yeast and bacteria contamination in draught lines

Visually Inspecting for Cleanliness

Visually inspecting a draught system for cleanliness is another good indicator of the health of the draught system.

Cleaning log. It is recommended that all draught system cleaners keep a cleaning log that is clearly visible to the retailer, the wholesaler, and the brewer. The cleaning log should show the last cleaning having occurred within the last two weeks and an overall two-week line-cleaning cycle.

Faucets. Visibly inspect the inside, outside, and vent holes of each faucet. The interior of a faucet can be scraped with the hard edge of a bar straw. Vinegar or butter aromas will indicate a bacterial infection.

Couplers. Visibly inspect the exterior of the coupler. Kegs can be untapped to allow the entire coupler to be inspected. Vinegar or butter aromas will indicate a bacterial infection.

FOBs. Visibly inspect sight glass, vent, and FOB stop. All components, inside and out, should be free of visible buildup. The sight glass should not have any haze and should be completely clear.

Jumper lines. Visibly inspect the flexible tubing in the draught system cooler. The exterior of the tubing should be free of any visible buildup. The tubing should be clear and free of color staining. Vinyl jumper lines should be replaced every two years.

Spill trays. Visibly inspect the grate and body of the spill tray. The entire spill tray should be free of any visible buildup. Vinegar or butter aromas will indicate a bacterial infection.

Note: Stainless steel is the recommended material for all metal components. Stainless steel will remain cleaner and is a more durable, longer-lasting material.

At this point there are few reliable and realistic ways to test for draught system cleanliness in the field. Because of this, the draught system cleaning and maintenance recommendations are designed to be preventive. Once a draught system becomes infected, it becomes extremely difficult – if not impossible – to completely remove the infection. The best defense against bacterial growth is to prevent it with recommended routine hygiene practices.

Off-Flavors in Draught Beer

When fresh and properly dispensed, draught beer will taste the way the brewer intended – clean, flavorful, and enjoyable. Draught beer is susceptible to damage from a host of factors, such as age, heat, and air. But the number one preventable factor affecting draught beer flavor and aroma is poor hygiene. Improper cleaning of draught system lines and components – from the coupler in the cooler to the faucet at the bar – can lead to significant changes in beer flavor, all of them unwelcome.

Over time, poor beer line hygiene will inevitably result in loss of sales due to customer dissatisfaction and necessitate replacing beer lines at great expense. Staying ahead of these potentially costly outcomes is key to serving great-tasting draught beer.

The Draught Beer Quality Manual lists the most common off-flavors that occur due to post-brewery unhygienic conditions and the mishandling of draught beer. While they are not health risks, beer-spoiling bacteria will ruin a beer’s flavor and aroma. By following the guidelines outlined in this manual, the occurrence of these off-flavors can be prevented.


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