How long does it take draft beer served using compressed air or a party pump to go bad?

Draft beer has become increasingly popular in recent years thanks to the proliferation of homebrewing and the availability of small, countertop draft systems. However, there are some important factors to consider when determining how long draft beer will stay fresh when dispensed using compressed air or a party pump system.

What is Draft Beer?

Draft beer, also sometimes called draught beer, refers to beer that is served from a keg or cask rather than from bottles or cans. Draught beer is pressurized by pumps, gravity, or compressed air which forces the beer out of the keg and into the glass. This method of serving beer is common in bars and restaurants.

The main difference between bottled/canned beer and draft beer is that draft beer is not pasteurized. Pasteurization is the process of heating beer for a short time to kill any potential microbes or bacteria. This gives bottled and canned beer a longer shelf life than draft beer, but can alter the flavor.

Since draft beer is not pasteurized, it is fresher tasting than bottled/canned beer. However, this also means it has a shorter shelf life and can spoil faster if not stored and dispensed properly.

Factors that Impact Draft Beer Freshness

There are several important factors that determine how long draft beer will stay fresh when dispensed with a party pump or compressed air:


Exposure to oxygen is one of the biggest enemies of draft beer freshness. Oxygen can cause beer to develop off-flavors and aromas, such as wet cardboard or skunky smells. Party pumps and compressed air will introduce some oxygen during dispensing, so minimizing exposure is important.


Warmer temperatures will significantly reduce the shelf life of draft beer. Ideal serving temperature for draft beer is 38–42°F. Higher temperatures will cause the beer to stale faster.

Light Exposure

Like oxygen, exposure to light can also cause draft beer to develop off-flavors and skunky aromas. Store kegs and serve draft beer away from direct light.

Keg Size

The size of the keg will impact how long the beer remains fresh. In general, the larger the keg, the longer the beer will last. This is because the ratio of beer to oxygen is more favorable in a larger keg.

Dips and Pumps

Using dirty lines or unsanitized party pumps can easily contaminate draft beer and cause it to sour or spoil. Proper cleaning and sanitation practices are essential.

Ingredients and Alcohol Content

Some beer styles, like hoppy IPAs, will taste stale faster than malty styles like stouts. Higher alcohol beers will also generally last longer. Stronger beers above 6% ABV will keep fresher compared to weaker beers below 5% ABV.

How Long Does an Open Keg Last?

An open, tapped keg of draft beer will usually last:

  • Commercial kegs (1⁄2 barrel = 15.5 gal):
    • Refrigerated: 45-55 days
    • Room temp: 30-40 days
  • Homebrew kegs (5 gal):
    • Refrigerated: 14-21 days
    • Room temp: 7-14 days

However, other factors like beer style, ABV, and exposure to light and oxygen can shorten or extend these general time frames.

Maximizing Draft Beer Freshness

Follow these tips for maximizing the shelf life of draft beer dispensed using a party pump or air compressor:

Use CO2 if Possible

While party pumps are convenient, using a CO2 system will keep beer fresher by minimizing oxygen exposure. Get the longest shelf life by using CO2 instead of air when possible.

Keep Kegs & Tubing Cold

Store kegs refrigerated as close to serving time as possible. Chilled beer lines will also help minimize foaming issues. Keep kegerator or jockey box cold if using a party pump system.

Clean Lines & Equipment

Dirty beer lines or pumps are a fast way to contaminate and spoil beer. Follow good sanitation practices and clean any equipment regularly.

Minimize Light Exposure

Direct sunlight and UV light can cause beer to develop a skunky, lightstruck flavor. Store kegs away from light and serve draft beer in opaque containers.

Watch for Signs of Spoilage

Signs that draft beer has gone bad include a sour aroma, buttery flavors, visible mold, overcarbonation, or a complete lack of carbonation. When in doubt, use your senses before serving.

Use Draft Beer Quickly

Try to finish kegs within 2 weeks of tapping for best quality. The fresher beer is consumed, the less deterioration in flavor and aroma.

Avoid Temperature Fluctuations

Big swings in temp from cold to warm and back can hasten staling. Maintain stable, cool temperatures as much as possible.

Troubleshooting Draft Beer Quality Issues

Here are some common draft beer problems and how to fix them:

Problem Potential Causes Solutions
Flat, lifeless beer
  • Old keg
  • Serving lines too warm
  • Improper CO2 pressure
  • Replace old keg
  • Chill beer lines
  • Adjust CO2 PSI
Overly foamy beer
  • Inadequate cooling
  • Dirty beer lines
  • Improper CO2 pressure
  • Lower cooler temp
  • Clean & sanitize lines
  • Reduce CO2 PSI
Cloudy beer
  • Yeast in suspension
  • Bacterial infection
  • Protein or hop particles
  • Let beer rest before serving
  • Disinfect system & replace keg
  • Use clarifying agent
Soapy, buttery flavors
  • Bacterial contamination
  • Fatty acids from dirty lines
  • Oxidation
  • Thoroughly clean & sanitize
  • Replace beer lines
  • Check for air leaks
Wet cardboard taste
  • Oxidation from oxygen exposure
  • Age of beer
  • Minimize O2 pickup
  • Drink beer more quickly

Frequently Asked Questions

How long does an unopened keg of beer last?

An unopened keg can last up to 6 months if stored cold between 38–45°F. Higher ABV beers may last up to a year. Over time, unopened beer will slowly oxidize and lose freshness.

Does draft beer go bad?

Yes, draft beer does eventually go bad once tapped. The signs of spoiled draft beer include off-flavors, sourness, flatness, or mold growth. An open keg should be consumed within 2 weeks for best quality.

Can you drink beer from an open keg after a month?

It’s generally not recommended to drink from a keg more than a month after first tapping it. The beer will likely have significant oxidation and staling issues, unless it was stored at very cold temperatures the entire time.

How long can an open growler last?

An open growler of draft beer will stay fresh for about 5-7 days refrigerated. Try to drink growlers within a week for best quality. Oxygen exposure when filling and improper sealing can shorten this shelf life.

What happens if you drink old draft beer?

Nothing harmful will happen if you drink spoiled draft beer, besides poor flavor. Old, oxidized beer may taste cardboard-like, have unusual aromas, or cause significant stomach upset. Quality really suffers the longer draft beer sits.

Keeping Draft Beer Fresh Longer

Following proper draft system design, cleaning and maintenance, pouring technique, and monitoring beer for freshness are the best ways to maximize how long draft beer stays tasty.

Investing in quality refrigeration, CO2 systems, and forward-sealing faucets will help minimize oxygen exposure. Drink kegs as soon as possible and avoid temperature fluctuations for best draft beer quality.

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