I'm getting annoyed by a leaking platy valve. I own a 2L Big Zip, and if I place it full at the back of my pack, the valve leaks, even when open. If I hunch, when climbing or reaching down, this changes to a constant stream of pressurised water, especially if the valve is open. Putting the bladder in a side pocket of my pack helps a bit, but doesn't solve the problem completely, and then I have a problem with significant change of load distribution when I use up the water.
Keeping the bladder outside of the pack is out of question, because one of primary reasons for my using it is that the water stays cool in summer and doesn't freeze in winter.
If I just press the bladder with my hand, the valve doesn't leak, so the pressure inside my pack has to be considerable, even though I don't compress it with too much force.
So, is my valve malfunctioning, or your's behave similarily?
Do you know which valves (camelback, stream, etc.) have best reputation?