We use the best in the business for soft flasks and bladders, which is Hydrapak. It's rare we see a defect, but these things do happen from time to time.
If you have a warranty request for a bladder or soft flask, please fill out this link here.
Flask and Bladder Warranty Link
If it's not a warranty and instead you need a replacement bite valve, bladder, or soft flask, please see this link for access to all available.