I dunno, I'm really picky about how flat things go especially it seems in plastic bottles. I consider plastic bottles to be effectively one-time use, like cans. A few hours seems about fine, but by the next day it's always too nasty. Doesn't matter if it's Coke, seltzer, whatever. Doesn't matter if it's 2-liter, 1-liter, 20oz bottle, 12oz bottle, just doesn't matter. So it could be just a matter of how picky you are about the carbonation. Or maybe it really is inferior carbonation, I don't know, but I know it's not just cheap seltzer that does it. Name-brand sodas are problematic as well, at least for me.
Been a while since I bought anything fizzy in a glass bottle that wasn't a single serving (Boylan's ginger ale has been a recent fave, but that's just 12oz bottles), so I don't really know how much that might help.
Been thinking about SodaStream again recently though as we've ramped up purchase of plain club soda/seltzer. Been buying it in cans for the moment. Been beginning a lot of sentences with "been".... ;-)
Yes. Mine lasts at least 3-4 days (sometimes even 7 days). The carbonation gradually fades.
Don't store opened seltzer bottles on their side - you are creating an ellipse with more surface area than a circle, so greater loss of carbonation.
And choose a good maker - not all seltzer is equally well carbonated....
3-4 *hours*? I have to think you're doing something wrong (like leaving it open for a long time before putting the cap back on?) I buy seltzer in 1-liter bottles and it last 3-4 days.
You could always try getting a SodaStream. Then you can re-charge your flat water whenever you like.
"is this abnormal??"
Maybe the cap was leaking "air", it sometime happen when the seal is first brake open when opening the bottle; water might not leak, but air and gas will.
It could also be depended on the "quality" of the carbonation process; or if it was natural carbonation.
That's why I buy small bottles instead of large ones.