Fizzy water without an explosion
September 3, 2012 6:06 PM   Subscribe

Are there safety data available regarding the maximum internal pressure of a 2-Liter PET bottle at standard temperature and pressure?

I like to make my own carbonated water with a CO2 tank and a 2-liter bottle. I would safely like to make it VERY carbonated. I have a pressure regulator that is set at 40 psi and use the bottles 10-12 times before throwing them away. I use cold water and shake the bottle for 1-2 minutes while attached to the CO2 tank. It works pretty well, but the water tends to go flat by the time I get down to the dregs. I would like to know how high I can set the pressure regulator and still feel comfortable with this operation. An initial internet search says 60-80 psi, but I would like to know if there is an industry standard as well. I am solely responsible for the results of your advice.
posted by surfgator to Food & Drink (7 answers total) 1 user marked this as a favorite
The industry standard appears to be the International Society of Beverage Technologists manual Voluntary Standard Test Methods for PET Bottles. I can't find it at any library via WorldCat. If you want to get a copy you'll need to talk to someone in the industry or join ISBT ($200).
posted by grouse at 7:14 PM on September 3, 2012 [1 favorite]

Are you sure that higher pressure will allow you to have more fizzy dregs? I've always assumed the dregs aren't fizzy because there's so much space for the gas to come out of the liquid once the bottle is nearly empty. I think you'd need to keep repressurizing.
posted by MonsieurBon at 9:19 PM on September 3, 2012 [1 favorite]

You may want to check out research done by people making water rockets


It looks like regular PET bottles for soda start breaking at around 130 PSI, though it's not clear that that can be done multiple times.
posted by gryftir at 12:26 AM on September 4, 2012

Can you buy vernors? Based on, um, empirical testing using the works and aluminum foil, Vernors 2-liter bottles are much thicker and stronger than regular soda bottles. (Vernors is a ginger ale sold primarily in the upper Midwest USA. It is very carbonated.)
posted by rockindata at 4:51 AM on September 4, 2012

Unless you exceed the PET's modulus of elasticity, it seems you could use these bottles indefinitely.

You could also do your own burst analysis since you have a pressure gauge and the failure mode is unambiguous. If it clusters around a range, back off significantly for your desired setting and fizz away. (You could also make some cozys from a stronger substance to contain any 'explosions'. My fizz bottle has chain mail around it, but of course, it's glass and makes better shrapnel.)

It would definitely be interesting to know if the degree of pressure influenced the quality of the "dregs" as MonsieurBon suggests. You may be solving the wrong problem and might benefit from pressurizing more and smaller bottles.
posted by FauxScot at 6:38 AM on September 4, 2012

Response by poster: Thank you for these helpful leads. I send a hearty "Cheers!" to ask metafilter with my glass of extra-fizzy water!
posted by surfgator at 9:47 AM on September 4, 2012

From my water rocket days, the burst pressure varies dramatically across brands, but unsurprisingly the thicker the plastic the higher the burst pressure.

Also they do not last indefinitely, fatigue and environmental degradation (especially UV light) reduce the burst pressure.
posted by trialex at 5:21 PM on September 4, 2012

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