Hot answers tagged equipment-care
Push the torn area up to the mouth and apply a bike tire patch to it from the inside (make sure it's dry). Then apply another patch from the outside. Where the two patches bond together will form a plug that should stand up better to water than a single patch.
You could try something like Shoe Goo or similar. Just dab on a small amount to seal the hole and ensure it doesn't stick to the opposite side of the hydration pack internally be keeping the sides separated until the Shoe Goo has dried. I repaired a small hole in a waterproof Ortlieb bag quite a few years ago and it is still holding up as a repair.
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