14 May
Posted in: Home Brewing
By    7 Comments

Home Brewing: Beer Not Carbonated Enough, How to Fix Flat Beer

After two weeks carbonating in the bottles, my second batch of beer was ready to taste!  I opened the first bottle, and poured the beer into a glass. To my surprise, the beer hardly had any carbonation in it, and pretty much no head!  What am I doing wrong. My first batch seemed to be a little under-carbonated as well. They are still drinkable, but it would be nice to get a little more carbonation in my beers.

Both of my first two batches seemed to come out under-carbonated.  I am not sure what I am doing wrong…

After transferring the beer from the fermenter to the bottling bucket, I boil 3/4 cup of dextrose with 2 cups of water for a few minutes. Then I let it cool and add it to the beer in the bottling bucket and stir it all together gently before bottling the beer.  When I fill the beer bottles I am pretty sure that I am leaving the perfect amount of airspace in the bottles (about 1 – 1.5″ of airspace at the top of every bottle.)

Am I doing something wrong in this step?  Do I need more Dextrose than 3/4 cup for a 5 gallon batch of beer? Am I better off just putting a teaspoon of dextrose into each bottle, rather than boiling it with water and adding it to the whole batch?  I heard this could allow bacteria into your beer if you don’t boil it first?

I would love for my beers to have a bit more carbonation, and a nice head on them. Can anyone tell me what might help me get some well carbonated home brewed beers?

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  • Have you been able to figure this out yet? I am having the exact same problem.

  • Cyle –

    Hey, I have not figures this out completely yet as I am still pretty new to beer brewing also. But, I just brewed a new batch of beer that I had in the primary fermenter for 7 days, and before bottling I just heated 1 cup of water with 1 cup of dextrose on the stove until it dissolved. I didn’t let it boil for too long this time. Afterwards I let it cool a little, then mixed it in with the beer after the beer had been transferred to the bottling bucket. This batch of beer was well carbonated within 7 days in the bottles.

    So I am not sure if a little extra dextrose and a little less water helped, or if not boiling the mixture for too long helped.

    The only other thing I can think of is that the other batches were in the primary fermenter for about 2 weeks, where this one that I just made was only in there for 1 week. So maybe the yeast was more active and able to carbonate better.?

    Not totally sure, If you come up with anything, please feel free to post another comment and let us know!


  • We’ve been getting into a homebrew project as well, and had a similar issue in our first couple of batches. We had a big surprise when we started using a kitchen scale in our brews – the 3/4c. measure that I used was nowhere near the right amount of dextrose by weight. Volumetric kitchen tools can’t really be consistent from material to material – our dextrose is pretty ‘fluffy’, so 5oz (the amount we were looking for) eyeballed out around a cup.

    I believe that 4-5oz is appropriate for most batch-primed 5gal brews, but there are wiser authorities out there. I would recommend you use a kitchen scale to measure your priming sugar, and don’t be afraid if you find yourself using quite a bit more.

    If I could, please allow me to recommend the Guide to Bulk Priming from Craftbrewers: http://oz.craftbrewer.org/Library/Methods/BulkPriming/SimpleGuide.shtml

  • Try carboantion drops. 1 drop per 12 oz bottle two for larger 22 oz bottles. No mesuring no boiling.

  • I don’t think your problem is the priming sugar. I actually think it’s a yeast problem. You need enough yeast cells to create the secondary fermentation in the bottle. When you pitch your yeast make sure that you have enough or make a prebatch to raise that cell count. I have come across this problem before (I am actually drinking a semi flat IPA now). I knew that when I went to pitch my yeast and the vial exploded that I may have problems.

  • I have been brewing for over a year. Have never had this problem using White Labs yeast. When using a packaged dry yeast have had this issue 2x. Back to White Labs

  • Thanks for your comment! After years of brewing, experimenting and mishaps, I have attributed it to the yeast not being viable enough when it went to the bottles.
    I used to transfer the beer from the primary to a secondary and let sit for a couple weeks or more. After over a month in the fermemters there just wasn’t enough viable yeast left to get going again and carbonate the beer fully. It wasn’t a brand issue with the yeast, just a time issue.

So, what do you think?