BeerBorg

I bottle in PETs still (740ML Coopers PETs, not the 1L Mr. Beer kind), so one bit of advice I can give there is after you tighten the cap, let the bottles sit for a while, and then tighten the cap again. You may be surprised how many you can tighten more even though you though they were tight the first time.

Yeah what mashani said. They always seem to tighten more after sitting a bit. I use 1L MB PET with the screw on top. I've had the random flat bottle back before I did the re-tightened step.

Monty

Bassman, I've been thinking on your OP. I opened a beer tonight that was bottled just shy of 3 weeks in my basement and the temp is down around 60-62 deg. right now and it has decent carb but I'd like to see a little more. This was batched primed and in glass capped. I agree with the others, you lost though the cap.

Although I rarely use PETs anymore, I got in the habit of savings caps from pop bottles and rotate them on a regular basis depending on how many I have. Not worth waiting for the caps to fail (and they will eventually) via flat beer before replacing them.

Thanks to all. I'm thinking that the PET cap is the culprit as many have suggested. I have been too gentle in tightening the caps for fear of stripping the threads. For fun I'll bottle mostly glass for my next batch but bottle a few PETs.