How do you know that you have leaky seals as opposed to just not having all of the batch of beer carbed up yet? Did you actually test the seals? or is it simply because some bottles are carbed and others aren't?
Often when a batch is not fully carbed, it's usually, just that ALL the bottles weren't ready yet, simple as that. Each bottle is it's own little microcosm, and they are all going to come to come up to carb in their own sweet time. You're dealing with yeast, a living microrganism and since it's alive it has it's own agenda.
When we say 3 weeks at 70 degrees, we say that that's usually the average minimum time it's going to takes.
If if bottles aren't ready by then, then you just gotta wait some more.
I've had beers that have taken 6-8 weeks before they were all carbed up. My Belgian strong took 3 months.
True you do have the variable of them being flippies, BUT if you bought them brand new it is unlikely that you got bad seals....it's possible, but I doubt it....
If you haven't already popped those bottles to test them, rather than rebottling them I would get a few latex gloves, cut off the fingers and use those over the seals on the bottle, stretching it down below the entire flipper mechanism (with large or extra large gloves the thumb, index and middle fingers work the best without tearing.)
Then I would shake those bottles to resuspend the yeast and stick them in a warm place for a couple weeks....if the "balloons" look like the have expanded the you might have leaks but if it doesn't AND you come back to the bottles and they are carbed, then more than likely those bottles were simply not ready yet, and may have been completely carbed up eventually anyway.
My experience has been that most carbonation problems are lack of patience and nothing is usually wrong. Although you do have more of a risk of actually having problem with the seals then if you were using crown caps...BUT having never bought brand new flippies AND never having replaced the seals on mine, I have NEVER had any leaky seals I have had fine carbonation over 5 or 6 bottling uses.. So I'm going to lean towards the not being done.
I write extensively about bottle carbonation here
Revvy's Blog, Of Patience and Bottle Conditioning.
But i the future when you bottle with these babies, you could consider doing some quality control by grabbing a few bottles out of a batch at random and using the "balloon method" on them to double check.
In fact I would mark these bottles with a grease pencil or piece of tape, and then make sure to balloon these as well as a dozen random samples from the bottles that you know worked fine....
Hope this helps.
