Why is My Beer Flat?

There’s nothing worse than opening your long awaited bottle of home brew only to find the beer flat and lifeless. Thankfully it’s easy to make sure this doesn’t happen.

why is my beer flat
If you understand why beer has gas in the first place, you can prepare the conditions necessary for it to form.

Why Beer has Gas

The bubbles in beer are produced by yeast as they convert sugars to alcohol and carbon dioxide gas during fermentation.

The gas is normally released from the fermentation bucket through the airlock (signalling to the brewer that fermentation is in fact taking place) so the beer has very little gas at the point of bottling.

If you try the brew at this point it will taste like flat beer.

How to Add Gas to Beer

To add gas to the finished beer, home brewers introduce priming sugar during bottling.

The yeast suspended in the beer ferment these sugars while inside the bottle. Because the bottle is sealed, the gas stays and becomes an integral part of the beer.

Generally, there are two ways of adding the priming sugar: as a solution mixed with the whole batch, or in small quantities put straight into each bottle.

Priming Solution

A sugar solution of approximately the same gravity as the beer is mixed (and boiled) and gently stirred into the wort. A typical mix of cane sugar for a 20 litre batch is approximately 110g.

It’s then left to settle for twenty minutes before bottling as normal.

Because you rely on dispersion for the sugar to evenly mix into the beer there’s potential for some bottles to be more carbonated than others.

Often, flat beer comes about for this reason. Don’t be impatient – allow the sugar time to mix into all parts of the wort.

It’s vital in this process that all equipment is sanitised and nothing is allowed to infect the beer.

Every time you mess with the beer there’s a risk of contamination from wild yeast or other bacteria.

Spoonful of Sugar

Some home brewers drop a spoonful of sugar into each bottle before syphoning the beer.

This method is easy but fairly inaccurate and can lead to flat beer or overly gassy brews.

Too much sugar causes excess gas which can potentially explode the beer bottles. The risk of contamination to the beer is slightly less than with a priming solution because no additional liquid is added.

Unless you’ve got a good reason not, avoid this method if you’re hoping for consistency between brews.

Carbonation Drops

Carbonation drops are a variation on the spoonful of sugar method.

These tablets of brewing sugar are put into each bottle to give a standardised dose. The drops ensure that each bottle carbonates equally and avoid the need to prepare a priming solution with the sanitising that that involves.

Of course, you’ll still need to sanitise the bottle tops and syphoning equipment during bottling.

The downside of carbonation drops is the lack of flexibility in terms of flavour.

It’s often interesting to add sugars that complement the beer, such as brown sugar to a dark bitter or honey to a summery ale.

On the other hand, the carbonation drops are flavourless so are a good general solution to a problem.

They’re possibly the easiest way of consistently carbonating home brew, but offer little flexibility.

I’ve Correctly Primed. So Why Is My Beer Still Flat?

If you knew all of the above already, have primed your beer correctly yet still wonder why you have flat beer there are a number of possibilities you could consider:

  • The yeast may have settled to the bottom – shake and see if that solves it (a solution from John Palmer)
  • The yeast may not have worked yet – it often takes up to two weeks for the yeast to finish production. This is often the case if the home brew releases gas when opened but has little head retention.
  • The temperature is too low for the yeast to work effectively. Either move the beers to a warmer area or wait longer.

If you’ve followed the steps above it’s just a matter of patience.

Now you won’t have to worry about flat beer again.

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  1. ken narbey

    Have been brewing for years with increasing success until two consecutive brews have failed to carbonate during secondary ferment. I know all the basics and have changed nothing in my system. Can you offer any advice ?

    • John

      Hi Ken,

      It’s strange that it should suddenly stop working if you’ve changed nothing in your system.

      Can you be more specific about your process: How do you add priming sugar? Do you bottle or keg? Is the secondary ferment in a cask? etc. Basically, what did you used to do to ensure carbonation?


      • George M

        I have been brewing for over 20 years without a hitch until recently. I keep getting flat beer – tastes fine, no fizz. The only change is that I am using a new silicon seal to stopper my Grolshe bottle (used for the last 15 years). Any ideas?

        • John

          Hi George,

          On the face of it it sounds as though there’s something wrong with your new seals. Have you tried a batch using ordinary bottles and metal caps, just to eliminate the possibility that the bottles are the problem?

          If not, are you leaving it long enough? I’ve had batches that I thought had failed to carbonate after three weeks but which after two months have turned out fine.

          Otherwise, feel free to leave more information about how you carbonate the beer as that may suggest another cause of the problem.


      • Ken

        It was my 3rd 5 gal batch. First two turned out better than I expected. On the 3rd batch I increased the extract to 8 pounds instead of 7, and I reduced the yeast to one packet of Safale 5 instead of two. I boiled 2 cups of spring water and added 3/4 cup of corn sugar, let it cool to room temp (70), siphoned into a carboy then to bottles. I did not stir/shake the carboy afterwards (wonder if that is part of the problem). Brewed 4/4/16, bottled 4/9/16. Today 4/24/16 still flat.

      • Ken Hakli

        Correction on my last post to you. I gave you the wrong dates, the brew was on March 19th, I bottled on the March 26th, Tuesday will be one month and beer is still flat. Should I try re-carbonating and how much sugar and/or yeast?

        • John

          Hi Ken,

          You could try recarbonating but presumably the sugar is still in the beer somewhere, so before you do anything, are you sure all the bottles are flat and it’s not just a couple?

          I don’t have a feel for whether the amount of priming sugar you added is a lot (I know grams and litres) but you potentially have some bottles packed with sugar, and you probably don’t want to add any more to those.

          If you decide to add more priming sugar, I’d mix all the beer together first and use a very small amount. If you don’t want to risk ruining the beer by exposing it to the air you could add a tiny amount to each bottle instead, and leave them somewhere secure in case any of them explode.

          If you decide to add more yeast, you only want a tiny amount.

  2. Just brewing my first home brew ever!! I’ve got to the stage where I’ve transferred to a pressurised barrel and it’s a case of waiting for things to settle and hopefully get some gas going. Getting impatient though.

    • John

      Hope it turns out well! It’s worth waiting as the beer tends to improve after a little time conditioning.

  3. Lee Darby

    Hi, I have just completed my first brew, from a starter kit bought for me at Xmas. I followed the instructions to the letter. It’s now 3 weeks since I transferred the bottles to the fridge after leaving them standing for 4 days at room temperature.

    I am getting different results from each bottle. Some are completely flat, others are fizzy, and one I opened yesterday had yellow lumps floating around in it like curdled milk. All of them are cloudy so far. I have opened 6 bottles in total out of the 22 I produced.

    Any advice on what might be happening please?


    • John

      Hi Lee,

      Was it a beer kit (a tin of hopped malt extract that you added sugar to) or a starter kit of ingredients that you brewed yourself?

      Something that jumps out from your question is putting the beers in the fridge so soon. It usually takes two/three weeks at room temperature (c. 21°C) for the yeast to carbonate the beer properly. You might have chilled the beers before they’d finished.

      Try slowly warming the bottles back to room temperature and leaving them a few more weeks. If the yeast have settled to the bottom you might need to gently shake them back into the beer as well.

      Another possibility, if you used priming sugar, is that it wasn’t mixed into all of the beer. Or perhaps the bottles with flat beer aren’t sealed properly.

      The curdled milk (does it look a bit like bread dough?) could be yeast that hasn’t dropped to the bottom. With time it should fall out, but the important question is whether the beer tastes and smells alright. If not, it may be something more unpleasant.

      In my experience, unless the beer’s clear when you bottle it cloudiness can take anything up to two/three, sometimes more, months to go. But it nearly always does, assuming the beer’s OK.

      The short answer to everything is give it time.

      Hope that helps!

      • Lee Darby

        Also, the lumps did look like bread dough yes.

        Just find it odd to be getting such different results from the same set up.

  4. Lee Darby

    Hi John

    It was a starter kit with a tin and 2 separate packets of yeast. I followed the instructions on the kit.

    I mixed the ingredients in the FV and left in a warm room for 7 days. After the 7 days I sterilised the 22 plastic bottles that came with the kit. I then added a level teaspoon of normal white household sugar to each bottle and syphoned the brew into the bottles, leaving approx 1 inch at the top of each bottle.

    The instructions said to leave in a warm room for another 4 days in the bottles then transfer to the fridge for 2 weeks. So in total the duration was 25 days from adding to the FV to testing the beer.

    Thanks for the help,

    • John

      Hi Lee,

      Yes, it’s strange that the results varied from the same starting point. That said, there’s usually a bit of variation just because yeast’s a live element that may not behave exactly as expected.

      Normally I’d leave the beer at least two weeks before bottling, and then expect to wait another two or three (at room temperature) before the gas builds up. I’d bring the beers out of the fridge for a few weeks and see if that fixes the issue.

      I’ve only brewed one beer kit (before starting brew in a bag) so am far from expert, but I think they sometimes underestimate the time for doing everything. In my experience time solves many problems.

      Hopefully you haven’t been put off brewing. It’s really great fun once you get into it.

      Good luck!

  5. Lee Darby

    Thank you John.

    No it hasn’t put me off.

    In fact, I’m going to purchase some ‘milestones crusader’ at the weekend and give that a whirl.

    I am going to take the remaining bottles out of the fridge this evening and transfer to the garage for a few weeks.

    I will buy a king keg at the weekend for the crusader to go into, and basically give it more time as you say. It’s a learning process.

    My friend began homebrewing in October and has successfully done 9 different brews so far, so we are getting quite into it together.

    All the best for now!


  6. John,

    I brew from a kit and do the two stage fermenation process. Then, after two weeks, it goes into a cornelius keg with co2 at 30 lbs for a week. The back down to 8-10 lbs and then tapped to drink. It seems flat. What did I forget? Gale

    • John


      I don’t (unfortunately) use Cornelius kegs so can’t really offer any advice.

      From what little I know, it sounds as though you’ve done it about right. Have you checked for leaks?

      Sorry I can’t be of more help.


  7. Jim

    You can improve on the ‘Spoonful of Sugar’ method by using sugar cubes. One cube = 1 tsp of sugar, no worrying about measurements or spilling sugar.

    • John

      Thanks for the tip, Jim.

      That’s a handy variation on the carbonation drops option, although personally I prefer to make a priming solution as that gives a bit more control. High or low carbonation depending on the type of beer.


  8. steven dodsworth

    Hi, I am brand new to home brewing and have just bottled my first batch of coopers canadian blond lager, I have followed the instructions to the letter, I primed the bottles with sugar and filled them yesterday, when I looked today the brew just looks completely flat with no bubbles in the bottle whatsoever. Is this normal at this stage, Thanks for your help.

    • John

      Hi Steven,

      Yes, that sounds normal. You never really see gas or bubbles through the bottle unless the beer’s been shaken up, even after a couple of months, so you won’t know if the beer’s flat or not until you open it.

      In my experience it takes about two weeks for the carbonation to complete. After a few days you will probably have gas and foam, but it won’t last long after pouring.

      The best thing to do is wait a couple of weeks and try then.

      Good luck!

  9. Evan

    Hi there. Me and a friend are brand new to home brewing and we just finished up a batch of India pale ale that turned out great. We strictly followed the directions with this first batch but now I want to try making a stout from one of the pre-made kits, but I want to try giving it a maple syrup flavor. Would I add the maple syrup in when I’m originally putting it into the fermenting bucket, or when I am bottling it? Also, exactly how much syrup would I need to make 23L batch? Could I do a mix of maple syrup and dextrose?
    Thanks a bunch for your help. Your website has already given me some interesting ideas.

    • John


      I’ve not added maple syrup to a brew before so can’t offer much specific advice.

      I imagine it would behave similarly to honey, which is best added after the main fermentation has finished. Before then most of the flavour is lost.

      You can add it directly to the bucket where it will ferment and increase the strength, as well as adding flavour. I expect you need a fairly large addition, to make up for the loss to fermentation.

      You could also add it at bottling, instead of using priming sugar. On it’s own I doubt this will affect the flavour that much but it’s nice to be consistent with ingredients. You could do a mix of maple syrup and dextrose, but you may want to test how much maple you’re getting first. The sugar won’t help if you’re short of flavour.

      I usually find with these things any advice you find won’t be specific to your ingredients and beer recipe, and that it’s best to carry out a few tests of your own.

      I like splitting batches and dosing each one with a different amount of whichever ingredient I want a test. That way, the next time I brew I have a better idea of how the ingredient performs and what I like.

      Sorry I can’t be of more help – good luck!


  10. Peter

    Hi, I have been making lager for a few years now with success most of the time. I now have a problem in that the beer is flat after a month. Its a Mexican Lager that made up the mixture as per instructions. I waited for two week for the first fermentation to finish. I left it longer then usual to let the sediment settle and reduce the amount in each bottle. I then add one carbonation drop to each bottle. I left the bottles in a warm place for a week before moving. It is possible that I left the first fermentation for too long and there was not enough yeast to start the second fermentation?
    Any advise?

    • John


      If it’s only been a month since you brewed it would be unusual for all the yeast to have settled out. Or did you do a long lagering stage?

      In any case, one week is a little short for the carbonation to take place. I leave it for around three weeks because usually some bottles take longer than others to complete. It could just be that you haven’t waited long enough.

      If that’s not it, are all the beers flat or just some of them? Are you sure there’s a good seal on the bottles?


  11. Scott

    I have brewed 5 different. Ale kits and 2 of them had the same problem with carbonation so what I have started doing is after first week of bottling I will ” gently ” turn the bottles over to unsettle the yeast and the let sit and settle back out and this has worked on past 2 batches, don’t shake though hope this helps!

    • John

      Thanks for the suggestion, Scott.

  12. helen oxley

    i have been brewing my own lager in kit form from fermenter to barrel with only 3oz of cane sugarto prime then after two days bottling. yuk flat horrid lager.after reading your site i had already bottled the lager,would it be ok to add caster sugar as primer in the bottles a day late ??

    • John

      Yes, you can open the bottles and add sugar if you’re sure you haven’t primed enough. Otherwise I’d leave it a bit longer to see if it improves first.

      Opening the bottles introduces another chance for the beer to get infected. It should be OK, provided you sanitise the bottle necks before and after opening, as well as all equipment and the new bottle tops.

      Hope the beer turns out OK!

  13. Bruce

    So I completely forgot to add the priming sugar sitting on the stove. Realized the next day and decided to let it ride. 2 months later on my quad hop 60 min IPA it’s flat. Out of frustration I gave it a shake a few days later I saw a few bubbles at the top of the bottle, and decided to give it a try. When I opened the bottle I heard a crisp pop top and it was fixed, good head on it. Through a little trial and error to prove or disprove this occurrence, I tried with some more bottles some with a slight shake some none at all. Truth be told the ones I gave a little shake to were carbonated the others were not. Not sure why but a temporary fix to a bonehead error. And I salvaged 45 / 51 beers.

    • John

      Hi Bruce,

      That’s an interesting story. Was the carbonation as good as it would have been if you hadn’t forgotten the priming sugar?

      • Bruce

        It was a little higher than normal surprisingly. My best guess is it somewhat reactivated any remaining yeast…

  14. Jason

    Home brew first try was a hefy extract. This Sunday, 2/22, will be two weeks. Problem is I have not seen any bubble activity in the air lock. I have added two packets of yeast. Advice?

    • John


      It could be that the gas is escaping through a route other than the airlock. Is it sealed into the fermenter or is the fermenter lid loose?

      It’s unlikely the beer wouldn’t have fermented unless you strayed far from a “normal” brew day. Have you checked inside for signs of fermentation?

      I don’t know if that helps, but feel free to reply with more detailed information if not.

  15. Rob Brown

    I’ve brewed bitter from cans for 10 years, always with good results. Lately, all my bottles are so gassy that I need 2 pint glasses to pour into. I always secondary prime with sugar solution into the fermentation vessel, any clue as to why my beer is suddenly so gassy

    • John


      If you’re doing everything the same way as you always have but suddenly the beer is too fizzy, it’s a mystery.

      Usually the cause is too much sugar, either from bottling early (before fermentation has really finished) or from too much priming sugar. It could also be that you haven’t cleaned your bottles well enough, and you have an infection.

      It could just be that you had a batch that for some reason went awry.

  16. Sue

    our home brew tastes a bit yeasty. 3 weeks after bottling. Carbonation is excellent. Will the yeasty taste settle out with time please ? Sue

    • John

      Hi Sue,

      The problem could be yeast mixed into the beer, in which case there’s a good chance you can reduce this effect by leaving the beer standing upright (in the fridge) for a few days before serving. When you pour it, use one smooth movement and leave the last 5-10mm in the bottle.

      Also, you haven’t mentioned how long you fermented for. A month or so gives the yeast time to condition the beer and settle out naturally before you bottle.

      Otherwise, the particular combination of yeast and fermentation temperature may have left a yeasty taste and it is part of the beer. You can test this by using another yeast next time, or fermenting slightly cooler.

  17. Greg

    Hi, I’m brewing a wheat beer from a can. Added wheat DME and brewing sugar, left it for 2 weeks, (which I always do) BUT checked gravity today and the beer seems gassy!!! Ok what did I do wrong? :(

    • John

      Hi Greg,

      I’m not entirely sure what you are asking. Would you mind explaining a bit more about what the problem is?

      Do you mean that the beer is still fermenting after two weeks?

  18. Greg

    Thanks for replying John. When taking a sample to test the gravity, it is almost clear and it seems slightly carbonated!!!! Could it be still fermenting or is it something else. Gravity reading today was 1.012

    • John

      It could be an infection, but it does usually seem ever so slightly carbonated. The gravity seems to indicate it’s fermented but you’d only know if it’s stopped by checking a couple of days apart.

      I wouldn’t worry if the beer is clear or not. That shouldn’t affect the taste too much.

      I’d just bottle it and see how it turns out. It may not be perfect but you can always make another batch!

      Hope it works out OK.

      • Greg

        Thanks John, I’ll leave take readings and hopefully bottle it over the weekend. Then another trip to the home brew shop :-) Thanks again. Greg

  19. jeanette

    Hi-I have made a few batches of beer from beer kits—the first one was great–second and third ones are flat….I used different water…would that make a difference? I have left this batch for 5-6 months….I brought up one bottle and it is cloudy–had some sediment on the bottom. What happens if it is infected.
    what should I do?

    • John

      Hi Jeanette,

      Without more detail it’s hard to know what to suggest.

      I’ve not heard of water affecting whether it is flat or not, so I wouldn’t have thought that’s the problem. Similarly, cloudiness or sediment shouldn’t be a problem either.

      If it’s infected it may actually fiz more than usual, depending how it is infected.

      Are you sure you used enough priming sugar, or if it was properly mixed in to the full batch? It could also have been that you didn’t have enough yeast capable or carbonating, depending what happended during fermentation.

      Sorry I’m not more help. Feel free to leave more information in case something stands out as an issue.

      Otherwise, your best bet may be to try another batch and find the problem by process of elimination.


  20. Alex R

    I think I may have killed off my yeast during bottling. It’s was my first time using a “no rinse” sanitizer and I noticed that I had left a few drops in each bottle before I bottled. I was just notified that wasn’t a good idea. I see now that my beer is flat after 2 weeks conditioning in temps ranging from 72-75 (f) degrees. Is there any way I can save my brew?!

    • John

      Hi Alex,

      Which sort of sanitiser did you use? That may not necessarily be the problem.

      If you have killed the yeast though, you should be able to mix the beer with some fresh yeast and pick up from there. You could either pour all the beer back into the fermentor, or try and add a little yeast to each bottle.

      I imagine it will be quite tricky to do this cleanly, as by opening the beer you run the risk of infecting it. But if you don’t like flat beer, it’s probably worth the risk.


  21. Samuel

    Hi I followed all instruction to the manual except I had a bit of a problem keeping a hi temp so it was low at 21 degrees in hot press in refrigerated 6, 7days ago I tried one and it’s flat but tastes good what should I do with the rest of them thanks in advance

    • John


      I’m not sure what you’re asking exactly. Did you add priming sugar to carbonate?

  22. brian cooper

    hi i have been brewing from kits for a few months now and i always keg the brew as soon as fermentation as finished can i leave the brew in the fermenter once it as finished brewing and for how long thanks for your help brian

    • John

      Hi Brian,

      By finished brewing, do you mean finished fermenting/bubbling?

      But yes. you can leave it in the fermenter for a while; in fact that will help condition it. You could leave it for up to a month without many problems.

  23. Richard Coleman

    I’m having a very similar problem to Ken Narby’s. Flat beer! Been brewing for years, always kits, always good. Leave it down for about 3 months after bottling. Don’t do secondary fermentation, do use a measuring thing for priming sugar. On the face of it I’ve changed nothing. So I’ll follow your tips and try more consistent storage temperature control. Great site, thanks.

    • John

      Thanks for the comment. Hope you find the problem.

  24. Mart

    Hi there John. Great site, very helpful.

    I’m on my first Coopers canned lager kit.

    Followed all instructions and everything has gone O.K. I got a great froth after adding the yeast which lasted for two or three days then I removed the krausen collar. O.G. was 1041 and now seems to be going nowhere at 1020. It’s been this level every day since day 6, now at day 10.
    Should it still be this high, and will it suddenly start to fall?

    • John

      Hi Mart,

      After 6 days the gravity has usually settled down, and probably won’t drop much more. 1020 does sound a bit high but sometimes that happens and you have to accept what you’ve got. Your gravity readings may not be especially accurate anyway, and the main thing is that it has fermented. It may be a bit sweet but it will be beer.

      I would leave it until it’s been at least two weeks, and then bottle.

      Hope this batch turns out OK and that you continue to brew.

  25. Grant Bryson


    I’m a first time brewer and my first beer has come out of the barrel with no fizz. Is there a way I can get some fizz into it and save what is otherwise a lovely tasting American IPA??

    • John

      Hi Grant,

      What sort of barrel are you using?

  26. Sally

    I’ve just made my first batch of lager, I added the hops and it said DO NOT STIR, now I’m ready to transfer to bottles, but the hops or maybe yeast has not dissolved and is now in the bottle, will this settle or have I done something wrong and ruined my lager. Have followed instructions to the letter! Thanks

    • John


      The hops won’t dissolve. When did you add them exactly?

      Your beer should be OK. Debris tends to settle to the bottom but hop leaves generally float. Perhaps you could pass the beer through a tea strainer to remove them.

      • Sally

        Towards the end just before bottling (I think) I did follow the instructions, it has now settled at the bottom of the bottle, so hopefully it will be OK. It’s pretty clear already so may try one on the weekend. THANKYOU

  27. Brian

    This may seem like a stupid rooky question, but here goes… When does the carbonation actually occur?

    I’ve just made my first batch of homebrew, Woodfordes Wherry. The secondary fermentation instructions were to add 1/2tsp of sugar to each 500ml bottle and keep the bottles in a warm place for a couple of days and then store in a cool place for a couple of weeks.

    Like, I’m guessing, everyone who has ever made beer for the first time, the first bottle was cracked on the appointed day, although I know the conditioning continues improving the beer for weeks or even months.

    The beer didn’t half taste good and had cleared nicely with a thin film of sediment in the bottom of the bottle, but it was flat as puddle water.

    I assumed that the carbonation would occur in the first couple of days when the beer was warm and the priming sugar was freely available and the cool period was for mopping up by-products of fermentation and clearing. Reading this and other forums it seems like it is a case of needing to wait longer and the carbonation occurs later on in the process. I’m confused.

    Did I leave it in the warm for too short a time or leave it in too cool a place maybe? The loftspace it was in could well have got close to freezing.

    I’ve tried inverting a couple of bottles and leaving them somewhere warm for a few days and now I’ll try a few days cool again to see if that works.

    Does the carbonation really occur after several weeks conditioning?

    • John

      Hi Brian,

      From your account it sounds like you didn’t leave the bottles long enough before cooling.

      You may find this post useful:

      I tried various lengths of time and found that about 6 to 9 days minimum was needed before cooling.

      Hopefully you managed to revive the other beers once you brought them back into the warm.


  28. Brian

    Thanks John,
    yes I managed to revive the beer by inverting and then keeping warm for 5 days. The degree of carbonation seems to vary a bit from bottle to bottle but they all now seem to be beer rather than tasty pond water.
    Next time I’ll leave in the warm for longer and control the amount of priming sugar a bit more.