006. Draft systems

Draft systems

A large part of providing beer service is dealing with draft beer systems. This section is an introduction to draft beer systems. We talk about the main parts of a draft system, basic operations, simple troubleshooting, and a little bit about system maintenance.

Stained Bar, Minus 1 Faucet by Callie Reed on flickr

Stained Bar, Minus 1 Faucet by Callie Reed on flickr (CC BY 2.0)

Some parts about draft systems are covered in more detail later in the syllabus. Other things are not important to us because, remember, compressed gas can be dangerous. So some things are best handled by a trained professional.

The reading material for this section was found in Draught Beer Quality Manual and Are You Draft Savvy? A little of the material came from Glastender operations manual.

Key elements

The draft system allows beer to flow from keg to glass.

There are 4 main elements to the draft beer system:

  1. Keg
  2. Coupler
  3. Foam on beer detector (FOB)
  4. Faucet

There are other elements, such as refrigeration, tubing, and inert gas. Each element consists of smaller parts. However, this section is concerned mostly with these 4 elements.

Keg – Kegs allow for storage and transport of beer. They protect the product from light and air, and also allow for rapid dispensing of the product. Kegs are usually made of stainless steel, but some kegs are rubber-coated, aluminum, steel, or plastic.

Sizes vary from approximately 5 gallons (1/6 barrel) to 15.5 gallons (1/2 barrel). The most common size of keg in the US is 1/2 barrel.

The keg has a valve onto which the coupler attaches. Never remove the valve. Kegs are pressurized and can be dangerous if handled improperly. Only trained technicians should service a keg.

Coupler – The coupler attaches to the keg valve and allows inert gas, usually CO2, to enter the keg and beer to come out of the keg. Basically, it lets CO2 in and beer out.

The beer line attaches to the coupler by a threaded “beer nut.” In the U.S., beer nuts are all the same, but beer nuts from other countries may be different. So be careful when attaching the beer line to a keg from another country.

Always check for leaks after you install the beer nut.

Foam on beer detector (FOB) – No, this isn’t the thing on your keychain. In a draft system, when the keg gets low on beer, the FOB automatically stops the flow. This prevents foam from filling the line. So when you change the keg, you don’t need to purge the line and fill it with beer again. This article explains it pretty well.

FOBs are especially common in long-draw beer lines, where purging the entire line could waste a lot of beer—and money!

However, some keg couplers have an FOB as a built-in feature. The coupler FOB has smaller parts that must be removed and cleaned separately from the beer line system.

Faucet – The faucet is the “tap” that dispenses the beer to the glass. Most faucets are suitable for both ales and lagers. In the U.S., most faucets screw onto a shank with a standard thread size, but faucets from other countries may be different. So be careful when attaching a faucet from another country.

The tap marker, commonly called a “tap handle,” screws onto the tap lever and identifies the type of beer being dispensed. Many states require a tap marker.

Align the tap marker so that the type of beer is clearly visible by both customers and employees. Many tap levers have a collar that screws up and tightens against the tap marker, keeping it in place.

Draft system operation

Serving draft beer will be covered in more detail in part I., section G (lesson 009).

For now just know that the draft system should have a standard temperature of 38° F (3° C). Warmer than that and the beer will foam. If it’s cooler than 28° F (-2° C) the beer can freeze, which causes cloudiness and an off taste.

Make sure to refrigerate kegs for 24 hours prior to dispensing, to prevent foaming. It takes a long time to cool a keg of beer. Glastender manual says: A beer keg that is allowed to heat up to 44° F (6° C) will take approximately 18 hours to cool down in a 36° F (2° C) cooler.

Remember from lesson 5, kegs must always be kept cold. So refrigerate kegs immediately after they’re delivered.

Do not try to adjust the gas pressure. Only draft-trained technicians should adjust the gas pressure to kegs.

Basic troubleshooting

More details will be covered in part I., section G (lesson 009), when we learn how to change a keg. And remember, never adjust the gas pressure, leave that for a draft-trained professional.

In the meantime, there are some simple things we can check when beer is pouring badly.

First, be sure that the beer has already been in refrigeration for at least 24 hours. It takes 24 hours to properly cool the beer throughout the entire keg. Improper temperature is the most common cause of problems. Warm beer foams.

Check that the coupler is properly engaged, correctly screwed onto the threads, and there are no leaks.

Look for kinks in the beer line between the coupler and the faucet. Undo any kinks or pinches.

Check that the FOB is properly set for service. Not every draft system has an FOB. A long draw system has a wall-mounted FOB, while some couplers have an FOB.

Draft system maintenance

Organic compounds and minerals from the beer attach to draft lines and affect beer flavor. Plus, it just gets nasty with fruit flies and grossness… yuck!

Many states require regular cleaning of draft lines.

Retailers may or may not clean their own lines. Sometimes the distributor does it or has another specialist do it. Nonetheless, it’s in your best interest to make sure the draft system is cleaned properly.

Every 2 weeks

The draft system should be cleaned every 2 weeks. A maintenance log should be kept to ensure that the draft system is cleaned at regular intervals.

Beer lines and associated parts should be flushed with cold water and cleaned thoroughly with an alkaline solution at the proper temperature and concentration. The cleaning solution should make contact with the lines for more than 15 minutes. Then the lines should be rinsed with cold water.

Take apart and hand-clean the faucets and couplers.

Every 3 months

Some parts need more thorough cleaning on a quarterly basis.

The FOB and couplers should be completely taken apart and manually cleaned.

Draft lines should be cleaned with acid to remove mineral buildup.

Whether we’re going to be serving beer from draft or from a bottle, we have to learn about glassware, how to get it clean enough for our favorite beverage, and which glassware to use for different kinds of beer. We’ll go over all of that and more in the next lesson.

Flashcards for this section

Based on the reading materials mentioned and my notes above, here are my flashcards for this section.

4 main elements of a draft system

  1. Keg
  2. Coupler
  3. Foam on beer detector (FOB)
  4. Faucet


Allows for storage and transport of beer.

Usually made of stainless steel.

Sizes vary from 5 gal (1/6 barrel) to 15.5 gal (1/2 barrel).

Has a valve to attach the coupler.


Attaches to the keg valve.

Allows CO2 in and beer out.

Beer line attaches to the coupler.


Foam on beer detector.

Automatically stops the flow when the keg is low on beer.

Saves beer—and money—by preventing foam from entering the lines, so you don’t have to purge the lines when switching kegs.

Can be wall-mounted, or part of the coupler.


The “tap” that dispenses beer.

Screws onto the shank.

Tap marker (“tap handle”) identifies the beer.

Standard temperature of a draft system

38° F (3° C)

How long must a keg be refrigerated before dispensing?

24 hours or else it will foam.

Who may adjust gas pressure to kegs?

Only a draft-trained technician may adjust gas pressure to kegs.

4 basic ways to troubleshoot a draft system

  1. Refrigerate the keg for 24 hours.
  2. Check that the coupler is engaged.
  3. Check for kinks or pinches in the beer line.
  4. Check that the FOB is set for service.

How often should a draft system be cleaned?

Every 2 weeks.

Every 3 months for a complete FOB and coupler cleaning.

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    I'm Nathan Pierce. I drink beer, I quit my job, and I'm planning to start a brewery. I also host a podcast about how to start a brewery. So I’m studying for Cicerone® Certification Program, Certified Beer Server exam.

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    2 thoughts on “006. Draft systems

    1. Thanks for explaining that draft systems need to be fully cleaned once every two weeks. In my opinion, it’s good to use a professional service to clean the 4 elements of a draft system, particularly the keg since it’s used for storage. A professional will know which areas need special attention and will already have all the cleaning supplies needed for the job!