How to Clean a Carboy – 8 Proven Ways

Making beer or wine or any other alcoholic beverage is a fun and rewarding hobby that many people around the world partake in. For most of us, the actual making of the beverage and of course the consuming of it are the best parts. However, an inevitable component to all of this fun is the cleaning of your equipment after brew day. As tedious of a task that it is, it is a crucial activity that you must perform or run the risk of spoiling future batches. One of the trickiest parts to cleaning is learning how to clean a carboy properly.

Whether you are using a plastic or a glass carboy to ferment in they both have notoriously small openings. Whereas most other fermenters have a wide opening where you can fit your hand and arm into them and apply some elbow grease to clean them, this is impossible with a carboy.

There are a lot of advantages to using a carboy so today we are going to share with you 8 options you can employ to clean your carboy and make sure they are ready for your next batch of brew.

Option 1 – Warm Water & Unscented Hand Soap 
A carboy surrounded by all of the products you can use to clean it. The words how to clean a carboy are to the left of the picture.
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Depending on how vigorous your fermentation was and how much and thick of a krausen line was left you can in many cases get away with simply using warm water and a squirt or two of unscented hand soap.

Fill your carboy up about ¼ of the way with warm water, squirt some of the hand soap in and give the carboy a nice shake. I always hold the carboy horizontal with one of my hands at the base and the other hand covering its opening at the other end.

Shake and swirl it around good. You might have to shake it for a while but in most cases, it will get most if not all of the dirt out. Dump it out and rinse the carboy as many times as it takes to get the soapy water out. It is very important to rinse the soap out well as any leftover residue can ruin your beer’s head retention.

Option 2 – PBW or Oxiclean

For those tougher stains, you are going to have to take it up a notch from hand soap and use either Unscented Oxiclean or PBW (Powdered Brewery Wash).

PBW, you can purchase at most online homebrew supply stores. Oxiclean you can typically pick up at any grocery store in the cleaning department, Amazon carries both of them as well.

Oxiclean is less expensive than PBW and it does as good of a job in my opinion. However, make sure you purchase the unscented version.

To clean the carboy simply add two tablespoons of either of the detergents into the carboy and fill them about a quarter of the way with warm water. Do note that if you are cleaning a plastic carboy then it is important to dilute the detergent in the water in a separate bucket or container prior to adding it to the carboy because the detergents when applied directly to the plastic can corrode them.

The first thing to try is exactly what we did with the hand soap. Give the carboy a good shaking and swirling. Another quick note, if you are going to hold the fermenter horizontally with your hand over the opening, I would recommend you wear some rubber gloves so the detergent does not harm your bare hands. When you are swirling make sure that the water touches all areas of the carboy.

Now you can take a look and see if it appears all of the grim has come off. If not then fill the carboy to the top with more warm water and let it sit for an hour. When you come back pour about half of the water out, give it another good swirl and then dump the liquid out.

You may have to repeat this process a few times until all of the grim has been removed. Once you are pleased with the results be sure to rinse the fermenter with clean warm water to ensure you get all of the detergents out of it.

Option 3 – The Long Bleach Soak

Rarely will it come to you having to use this option. In most cases, PBW or Oxiclean will do the job for you. However, for those overly tough stains that you just can’t get rid of them, it is time to break out your household bleach. I only recommend you use this on glass carboys as plastic fermenters can absorb the bleach and ruin your next batch by imparting its odor to your brew.

Pour in approximately 4 ounces or 118 ml of bleach and then fill your carboy up to the top with warm water. Let it sit for at least 12 hours, the longer you can let it sit the better. When you are done it is important to thoroughly rinse your carboy with water to make sure to get rid of all of the bleach.

Option 4 – The Bristle Brush

If none of the above work it is time for good old-fashioned elbow grease, however, the problem is you can not get your hand into a carboy due to its small opening, as such you need a carboy brush. These brushes have a long-wired handle that you can bend and manipulate to get into those difficult areas. The bristles are plastic.

Never use these brushes on a plastic fermenter as you can scratch them. Those scratches are places that bacteria love to hide in. Although glass should not scratch, some overcautious homebrewers will fit a sock over the bristles just to be extra careful.

Now fill your carboy halfway with warm water and add either PBW or Oxiclean; give the mixture a good stir with your brush and get to work scrubbing with the brush.

Once again when you have finished, be sure to rinse the fermenter with clean water ensuring to get all of the detergent and grim out.

Option 5 – A Rag

If you don’t have a brush or are just hesitant to use it or your carboy is plastic then you can use the rag method. Soak your rag with PBW or Oxiclean and insert it into the carboy. You can also add a small amount of warm water with some detergent if you like. But do not add a lot of water because you do not want the rag floating around. Now shake and swirl your fermenter. The rag will help remove any of the touch grime that has formed on the sides.

Option 6 – Ice & Sea Salt

If none of the other options work to clean out your carboy this is a handy method that works like a charm. Get yourself some sea salt as it is more abrasive than normal table salt. Mix two tablespoons of it in the fermenter with two cups of ice. Once again start shaking your carboy vigorously. You may find that the salt melts the ice and that you will need to add some more. You will be surprised at how well this method works.

Option 7 – Rice & Baking Soda

This concept is similar to the ice and sea salt, you can use them interchangeably depending on what ingredients you have on hand. In your carboy mix 3 tablespoons of baking soda with half a cup of rice and add just enough water to allow the mixture to slosh around. Baking soda is known for being a great cleaner and the rice acts like bristles on a brush but are not abrasive. Give the carboy a good shaking and swirling.

Option 8 – The Mark II Keg and Carboy Washer

At my brewpub we served our beers in corny kegs, they can be as tricky to clean as a carboy and we used many of the same options for cleaning that we have discussed today. However I came across these Mark II Keg and Carboy washers while looking for alternative methods for cleaning, as we had a lot of kegs to clean, and doing so manually took time.

We picked up two of these units as they are quite inexpensive. I’m pleased to report they do a really good job of cleaning kegs, fermenters, and carboys.

Basically, they are a tray that you fill with water and a cleaning agent such as PBW or Oxiclean, in the center they have a tube that runs vertically, it has holes all through it. You place your keg or carboy over top of this tube and then plug the unit in. It is very much like a mini CIP system (clean in place) that the big craft brewers use to clean their equipment. The tube now inside the carboy sprays the solution all over the inside of it.

This method is by far the simplest and most effective out of all the ones we covered today. If you can afford the $99 price tag I highly recommend it.

Frequently Asked Questions

How do you sterilize carboys – Star san is a no-rinse sanitizer and it is without a doubt your best friend when it comes to sanitizing or sterilizing any of your brewing gear. When I am done fermenting I clean my fermenter as we have discussed and then I fill it up with a mixture of water and Starsan and let it soak until the next brew day.

How do you dry a glass carboy – As you just read I typically do not as I brew on a regular basis so I keep them filled with starsan until the next brew day. However, if I were to take a break from brewing and wanted to store my carboy for a while I would either purchase or make a carboy dryer.

This is a very simple piece of equipment that has a sturdy base and a wide opening in the top that fits an upside-down carboy perfectly. It allows any liquid to drain out and allows for air to flow inside of it to dry the inside. They are very similar to bottle drying racks you might have seen. The same principles apply.

What is Powdered Brewery Wash – PBW is an alkali cleaner that is good for the environment and safe to use. It is used by many commercial brewers and homebrewers for removing tough hard to get at stains and organic soil build-ups. It is extremely effective at cleaning brewing equipment such as brew kettles and fermenters.

How to Sanitize a Carboy with Bleach – Bleach is a decent option for sanitizing all of your brewing equipment. It is readily available and does not cost much to purchase. Simply mix 1 tablespoon with 1 gallon of water into your carboy. Give it a good shake so that all surfaces are touched by the mixture.

Be careful not to get any on your hands, rubber gloves are recommended. Let the solution soak for at least 30 minutes and then proceed to rinse the carboy out with hot water.

You now know exactly how to clean a carboy and are all set for your next brew day.  If you have any questions on anything we covered here please do not hesitate to ask me in the comment section. And let us know what is your favorite way of cleaning your equipment?

Big Robb with a pint of home brewed beer
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Cheer, Big Robb is Out!

P.S. If you want to get access to my best-selling beer recipes from my brewpub I am giving 5 of them away on the side of the blog or the bottom on a smart device. Enjoy!

2 thoughts on “How to Clean a Carboy – 8 Proven Ways”

  1. I wouldn’t recommend pouring boiling water into a cool or cold glass carboy. The thermal shock might cause the glass to break. Hot water from the tap is OK, though, in my experience.

    Some yeasts can create a bio film on the inside of a carboy and contaminate the next batch. I use a brush to help clean anything visible from the inside of the carboy, then I fill it with water with a tablespoon+ of bleach per gallon and let it sit for several days, then I rinse multiple times with small amounts of water before using it again.

    • Hey Neal thanks for the tips man, and I agree with the boiling water, changed that out. Cheers


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