The Scoop On Using A Plastic Carboy For Wine And Beer

The "PET" plastic carboy has been around for years...


Thousands of gallons of excellent wine and beer are made annually by creative home brewers using these carboys. Me included.

Backing that up are all the positive reviews on many suppliers sites. So they certainly have their place for the home winemaker or brewer. Especially for short-term storage.


Image showing three kinds of PET carboysThree options of PET carboys to choose from

They can usually be found in:

Ribbed and smooth

  • 3-gallon
  • 5-gallon
  • 6-gallon

Wide-mouth

  • 6 and 7-gallon sizes

And are:

  • BPA-free
  • DEHP-free
  • plasticizer-free
  • tasteless
  • odorless
  • and clear


Best Place to Buy a PET Plastic Carboy?

Infographic of a truck symbolizing a supplier

These retailers have been selling the PET plastic carboy for many, many years. They are the most trusted suppliers in the brewing and wine making circles. Check for the best prices or shipping deals when you're ready to buy and save some coin.

  1. morewinemaking.com
  2. homebrewing.org
  3. amazon.com





What's So Good About Using a Plastic Carboy?

There are some distinct advantages of using a plastic carboy instead of glass:

  • cheaper to buy
  • lighter in weight so shipping costs are lower
  • easy to move around - at least when empty
  • you can buy them with a spigot so draining/racking is a breeze - though it's more nooks and crannies for beasties to hide in
  • they will accept a bit of abuse on the outside without cracking
  • they are made of "PET" which is the most recycled plastic in the U.S.



If you're just getting started in wine making these carboys will do just fine and are a great place to start. Here's a look at the pros and cons of glass carboys vs plastic in more detail.

Smooth-Sided Carboys VS Ribbed-Sided Carboys

The PET carboys with smooth sides are generally preferred. In my experience - there are no ribs to "catch" dead yeast and crud which makes them easier to clean.


Infographic comparing smooth wall PET plastic carboys to ribbed carboysSmooth carboys versus ribbed carboys

An added bonus is being able to watch your fermentation through a completely unbroken surface. I like that.

I get that the ribbed carboys are designed for strength. That's what ribs do. It's just that this can also be accomplished by going with a heavier wall thickness.

The smooth sided carboy also has a better surface to attach a heat pad to when fermenting. The pad can do it's job more efficiently because it sits flat on the entire surface instead of just contacting the top of each rib.

A brew belt works fine on the ribbed models though because they're narrow enough to fit between the ribs.

And if you use a stick-on thermometer make sure the ribbed carboy has enough vertical flat surface to stick it on.

The pros and cons between wide-mouth and standard neck carboys can be found here under glass carboys.


Is Pet Plastic Food-Contact Safe?


PET or polyethylene terephthalate is the same plastic used to make clothes, bedding etc. It's polyester. It's only called PET when it's used for storage or packaging containers. Like a PET carboy or drinking bottle.


There are different grades of PET and even coatings that can be used on top of the plastic. These "pure" resins and veneers are what makes it food-contact safe or not.

All PET plastic is not the same. PET plastic water bottles are for one-time use only. PET carboys are for repetitive use. So you need to follow the manufacturers suggested use.

The recycling symbol on the bottom has nothing to do with it's use. That's for recycling purposes only. There's more info about that on my food grade buckets page.

If the label or retailer says it's food grade then you're good to go. If you come across a used carboy second-hand then be very wary. In fact unless you know it's history you probably shouldn't use it.

Beware of any older carboys that are not made of PET plastic. Stay away from them as they are porous and nasty for your health.


Will Air Seep in Through the Plastic and Ruin Your Wine?

Infographic showing oxygenation through PET carboysWill your wine or beer oxygenate in a PET carboy over long-term storage?

Short-term Storage:

PET plastic has a very low permeability coefficient. That means oxygen can't work through the plastic carboy wall to ruin a tasty batch of your wine or beer (for short-term storage).

Barrier coatings and oxygen scavengers are used to help accomplish this over the short-term and at certain temperatures. Be aware that higher temperatures will allow more oxygen transfer through.

Long-term Storage:

Long-term storage of beer or wine in PET carboys is likely not a good idea.

So... what exactly is accepted as long-term?

That's where the fog rolls in. My comfort zone is that any wine or beer that spends longer than 3 months in the carboy is long-term. For some people it's 6 months and up.

You'll have to decide for yourself. Just how much air will filter through the plastic and it's barrier coatings is debatable.

Neither is there scientific evidence of plastic toxins leaching out and migrating into your tasty batch of wine within a specified time period.

But - plastic is not nearly as hard as glass. And acids and alcohol are very strong compounds.

Let your common sense prevail here.


Can PET  Plastic Degrade?

Infographic showing the sun's harmful uv rays on PET carboysKeep your plastic PET carboys out of the sun to avoid uv ray damage

Everything degrades to some extent over time and it can happen quicker in certain circumstances. If you're going to use a PET plastic carboy then here's some guidelines to follow:

  • don't expose to light (especially UV rays) - polyester or PET absorbs UV wavelengths and loses it's mechanical properties over time
  • keeping plastic cool is smart too as extreme temperatures can accelerate degradation of plastics
  • use it for short-term storage only - such as 3 months or less
  • keep temperature fluctuation to a minimum
  • don't expose it to acetic acid (vinegar) - at 5%+ the acid will start to deteriorate the plastic slowly

I mentioned acetic acid only because wine can turn into vinegar and some people make it in carboys. There are other chemicals that will degrade PET but nothing to worry about if you're only making wine and beer.

The jury is still out on whether you need to toss the PET carboy into the recycling bin after X amount of years of normal use and care. At some point the plastic will break down and start to degrade. 


Clean and Sanitize PET Carboys Carefully!

Infographic showing how to clean PET plastic carboysClean PET carboys without scratching them

Cleaning

  • use water no hotter than 125°F (52°C)
  • use Free and Clear Natural 2X 7th Generation laundry detergent or (2nd choice- B-Brite, PBW) diluted for routine cleaning
  • mix detergent/water in a separate container and then add it to the carboy (stirring can scratch plastic)
  • don't use brushes or scouring pads - add only the detergent plus a small soft rag (scratches in plastic harbor bacteria and can ruin a batch of wine)
  • use a stopper and soak upside down for stubborn stains
  • don't let the detergent sit in the carboy for more than a few hours
  • rinse with clean water immediately after washing



Sanitizing

  • sanitize normally with potassium metabisulfite, Star San etc.
  • drain completely right away and air-dry OR clean rinse with very clean water and air-dry


 Most of the guidelines above vary by manufacturer but if you follow these you'll be fine.


The Common Sense Approach!!!

Wine making and beer brewing communities are a unique bunch. We're storing alcoholic beverages in a container for sometimes many years. If you've decided to use a plastic carboy then just use common sense.

There are no long-term studies (2 years+) done on the storing of alcohol in plastic (PET) that I could find. Err on the side of caution and use:

  • glass carboys and demijohns
  • stainless steel
  • or oak for extended storage

Your reward is tasty wine or beer... and good health!



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