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PET bottle failure - how long should they last?

King Ruddager

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Came home to a house that smelled of beer today and, sure enough, one of my PET bottles has cracked through the bottom. Beer is everywhere, at least four of my boxes are ruined ... it's a disaster sad


I thought that PET bottles were supposed to last a long time. Was I mistaken? Some of mine would be three years old now but the one that broke was showing no signs of cracking in the bottom like some of the older ones were. Also, I thought that PET bottles were supposed to almost never explode as they are permeable to CO2.


So, what's the deal?


(no, I'm not switching to kegging)

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From all the reading I've done, the biggest issue with PET bottle failure is cleaning them with water that is too hot. Apparently, the water should be no hotter than you can comfortably bear to dip your hand into. Dishwashers are a no-no.



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This is from the Coopers FAQs:


The Coopers DIY Beer Kit contains thirty 740ml PET bottles. These bottles are also widely available as a separate item (in boxes of fifteen).


PET stands for polyethylene terephthalate, which is the same plastic used to make soft drink (soda pop) bottles.


Since 2000, Coopers has included PET bottles with the starter kits (initially the Micro-Brew Kit and now the DIY Beer Kit) rather than the traditional crown seals and capper because it was becoming increasingly difficult for new brewers to obtain sturdy crown seal bottles. Today, most commercial beer is packaged in single use glass bottles, which are too thin to stand up to the rigours of continual washing and capping.


The majority of PET bottles are subtly porous and a beverage held in PET will eventually go flat. However, Coopers PET bottles have a nylon barrier, reducing the rate of ingress of oxygen and the loss of CO2 for up to 18 months. The re-usable caps have a tamper evident collar that breaks off after the first use. This does not affect the airtight seal. When the caps eventually wear out, replacement caps can be purchased separately.


Note: PET is temperature-sensitive and should not be cleaned using hot water.


A beer, such as an Imperial Stout, intended to be aged for 2 years or more, should be bottled into sturdy glass designed for re-use. With this in mind, Coopers also produce Original Pale Ale, Sparkling Ale and Best Extra Stout beverages in sturdy 750ml glass bottles. These bottles have a lip designed for a prise-off crown seal and weigh more than 500g empty! They are an excellent option for brewers and sauce makers, alike.

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I usually rinse them in hot tap water.

Mind you, the hot water in our place goes through a temperature control, so it's never boiling hot; in fact I just checked it, & it runs at 65c.

I half fill them with the hot tap water first, then simply tip them.

Then I do it again twice, giving them a vigorous shake with the lid on, before emptying.

Other than that, usually on brew day I soak them in laundry soaker for an hour or so, then rinse with cold tap water; I use the FV, the tap & wand to fill the bottles.

Obviously I also give them a quick rinse in no rinse sanitizer too, making sure to empty out as much as I can.

So far I haven't had any major issues, but I have noticed my brews aren't carbonating as well as they used to.

Not a real problem, as they're not flat, just not as gassy as commercial brews or my first few batches.

I've come to accept that my beer isn't overly gassy, & to be honest, it's easier to drink when you're not continually belching from excess gas.

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Been brewing for a long time but new to club.

I have never washed my pet bottles in hot/warm water & have never had a problem with pet bottles.

I also use carbanation drops.

i also wash & re-use the caps in cold water

I use sodioum percarb for washing,make a mix up

Soak for a while then clean with brush ,rinse thouroughly then drain

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I'm guessing just wear and tear on the bottle resulted in a weak point and it gave up the ghost. Could also be a contamination in that bottle only, resulting in the remaining sugars that the yeast don't consume, being eaten by the wild yeast or bacteria.


For Eg: Say your FG was 1010, when you add priming sugar, you bump it up to approx 1014, when finished carbonating, it should be back to exactly 1010. The contamination can bring the gravity down to 1000 or lower, resulting in a huge amount of gas in the bottle. Standard carbonation of 2.5 volumes, is 2.5 atmospheres, approx 2.5 times 15 psi. So say 40psi, or the pressure in your sports car tyres. Imagine the contamination taking it to 100psi or higher. She's gonna blow Jim...


Pretty rare if proper sanitation is followed, but this type of thing is one of the reasons why (I guess) Coopers have moved to the PET for the kits. If you do blow some bottles, you will have a big mess but no flying glass.

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  • 1 month later...

Another Viking busted his way out of the arse-end of a PET bottle yesterday pinched I'm going to ...


  1. Continue to "retire" bottles that look stressed at the bottom
  2. Only ever use cold water on my PET bottles
  3. Never prime at a rate more than 6g/L


About half of my beer is more than 5 months old at the moment, so I've got to start allowing for extra carbonation in the late, late, late stages. Having said that, the explodey ones were only bottled three moths ago. So far both explosions have been from the same batch (my latest Viking Beer) which is ... good? Consistency is always good, right?

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Ahh Mr. King, to have bottles 5 months old. What dreams are made of. joyful Perhaps I'm just an old soak coz I'm always chasing my tale trying to get ahead. I did at Christmas time so suppose I should be able to all the time.


Never had any problem with the PET bottles though. And I do sometimes use hot water, so won't do that anymore. Just bought 2 more cartons of PET's coz I'm sick of trying to put caps on twist off bottles. Get a sore hand out of it. A hell of a lot quicker bottling with PET. Had an occasional one turn out flat, but had that with glass too. I use carb drops so maybe I missed priming one now and then.


Actually enjoying probably the nicest Coppers Pale Ale that I've ever made. (My favourite tipple tongue ). First time it's come out with the cloudy finish that I was used to drinking it off the tap. Bloody great mate.biggrin

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Ahh Mr. King' date=' to have bottles 5 months old. What dreams are made of.[/quote']


I went through a period of buying bottles and brewing like crazy a year or two ago, just so that I could be in this position. I think I have 210 of them now! I vary between having about 45-75% of them full most of the time.


are you using coopers PET bottles or a different brand?



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A mate gave me a box of PET bottles which were a different brand to Coopers. They looked and felt thinner and were a paler colour than Coopers, so I tossed them. I wasn't going to trust wasting 23 litres of beer. Why use anything but the tried and true reusable PET bottles made especially for beer by Coopers?

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