As a relatively recent convert to hydration systems, or platypi (it seems Platypus is to hydration what in British English, Hoover is to vacuum cleaner) I’ve had to learn how to look after them when they are not being lumped about in my pack.
It might sound strange that they need any “looking after” at all, but they do. Or else you end up sucking mildew flavoured water through a black spotted tube.
The usual handy hint to prevent that is simply to store them in a freezer. But in a small kitchen, with a very small freezer, the food has to get first priority. So no freezing for our platypi except in-use on the hill (for which a neoprene cover, that covers the bite-valve, combined with blowing back into the bag, works very well for preventing a freeze-up even at minus-a-lot Celsius).
So I’ve got in to a very simple routine for making sure they stay mould free:
When you get home, fill the bladder with really hot water from the tap. Not from a kettle. It might work, I’ve not tried it, but I have a feeling that boiling water would damage the bag (anyone know different?). But use very hot water never the less.
Hold the bag above the sink and squeeze the bite valve until a lot of really hot water has had a chance to clean out the tube. It needs to run for a good ten seconds I reckon, since the first run through the pipe will cool by the time it gets to the bite valve.
Then drain it out and shake out the excess drops of water.
The last trick relies on having a bite valve that will pop off easily, or at least dissemble without too much of a struggle (like the Source variety – whose bite-valves I favour) and a bag that opens at the opposite end from the tube (like a Platypus Big Zip or Source Widepac): Remove or dissemble the valve to get a good airflow up the tube, stick the tube out of a window (perhaps a second floor window, in case you forget its open and leave the house!) and prop open the bag with something.
The breeze blowing through the window will get pushed up the tube, and usually dries the bag in a few hours even on a still day.
With a bone-dry bag, there’s nowhere for the black mould to grow – and you get a happy, healthy platy.