G'day Jane,

The valve is tightly on to prevent leaks, it can be difficult at first to pop this off. A few others have recommended to slowly pull the clear plastic valve away from the bladder and it should peel off quite easily. You could try to get a bit of your thumbnail or round-ended butter knife or screwdriver to help lift this off.

G'day Sharron,

The spout system can be a bit tricky the first time you remove it to fill up but it's super easy once you know the technique. The black cap pops off effortlessly but the valve is quite tight to prevent leaking. Using gentle pressure, slowly pull the clear plastic valve away from the bladder and it should peel off quite easily. Maybe try to get a bit of your thumbnail underneath as leverage. 

G'day Callum,

The Sea to Summit Pack Tap bladder is made from a double layer tough Mylar which is a combination of plastic and foil. Similar to the bladders in the boxes of water, except a little more durable and tougher.