The whole selling point of big zips is the BIG ZIP at the top of these babies - It allows easy filling and also easy cleaning. The only problem is that the zip is not quite as reliable as Platypus make-out. I've seen people walking along as if their backpacks waters have broken beecause a bit of weights shifted in the pack, put just a teeny bit too much pressure on the Big Zip and causes a good 1 litre plus of water to erupt.
Pass the tissues.
Like all Plats they're a good idea - the plastics thick and doesnt puncture too easily, they DO clean easily and WILL take boiling water but DO NOT microwave them to force the final few blebs of water out of them - the smells similar to what losing a PVC-wrapped Donkey in a vat of conc sulphuric acid must be like (don't ask)
Yes, the let-downs that zip. Its just not trustworthy. I myself have many times spent an age massaging the zip, imverting to test, massaging it closed a bit more, invert .. SPLOOOSH.
How can a waterbottle have trust issues? Buy one, not acquire the nack and then see.
(Written by: Requiem)