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Why does a plastic water bottle suck inward on itself, with it being full of water and unopened for years? Answered


PET plastic isn't necessarily gas proof long term but it would take some external lack pressure to suck air out - I go with pressure or temperature changes over time.

Bettix's link shows graphically what is going on.

DM6's link is dead, but here is a replacement:


The important section is labeled: Moisture Vapor Migration

So I looked at several plastic water bottles to see what they are made of. Use the plastic recycling codes as a guide:


What I found was there was a mix of (1) PET and (1) PETE

From https://en.wikipedia.org/wiki/Polyethylene_terephthalate in the Physical Properties it says

It makes a good gas and fair moisture barrier

Fair, not Good.

So amazing as it seems, the water is very slowly migrating through the plastic (in microscopic amounts) and when it gets to the outside it evaporates. Air from outside does not go in the opposite direction to replace the water. As the bottle is still sealed, the reduction of water in the bottle causes it to collapse so that the pressure inside the bottle matches the external pressure.


1 year ago

http://www.bettix.co.uk/plastics-fluorination/why-fluorination-the-problem -Here's the only solution to stop the paneling of bottles, get your bottle fluorinated.


3 years ago

I am wanting to know the answer to the same question. I believe this experience of collapsed unopened water bottles is a little more detailed than we are told. Does the plastic degrade? Lots of people probably have cases of water that have had this experience after storing for a few years.

Is it dangerous to consume?


7 years ago

Has it been moved to a lower altitude?

Because leaving water in a plastic bottle for years just SUCKS! Don't do it.

Lots of reasons, I think most likely is nacho's suggestion that the bottle is permeable and lets some gas out.

Gasses dissolve in the liquid, thus acting as a liquid and not exerting their pressure on the bottle walls.

The plastic in the bottle could be actively 'eating' the gasses - I have no grounds to support this theory, but given that some plastics off-gas, it makes sense they might react with and store some gasses.

. Could be that some germs have used up all the Oxygen, Nitrogen, &c.
. Maybe plastic bottle are ever so slightly gas permeable and the gas gets pumped out with temperature fluctuations and/or variations in pressure.
. Magic!