Beer going flat after chilling

[nztayls]

Okay, so I have finally made what I think is a very drinkable Witbier, after a couple of false starts. But now I am faced with a new problem, in that it appears my beer is going flat when chilling it.

After about 3 weeks of conditioning, the plastic bottles were rock solid to touch. You couldn't squeeze them, so I figured the carbonation had worked. I then chilled a whole lot of them down, and after a couple of good ones I have noticed that several have been flat. I have now started squeezing the bottles as I get them out of the fridge, and have noticed that a number of them seem to have some give in them, that wasn't there before. The only thing I can think of is that the cold temp of the fridge is shrinking the the necks of the bottles more than the screw tops, and thus breaking the air-tight seal. But I'm not sure.

Anyone else experienced this sort of thing?

 

[Cyclman]

Yes, plastic bottles can leak @ the cap, it is a common complaint.

 

[JRems]

The co2 is being absorbed into the beer when chilling. It's normal. Does it taste flat when you drink it? When it's warm it's probably close to 30 psi. When chilled it's closer to 10psi

 

[cooldood]

I agree warm the beer up a bit and I bet it has plenty of carbonation.
I use pet bottles all the time and never have problems