Ortlieb bladders and bags
Ortlieb live up to their reputation of strong, durable and practical products with their water bladders. We have had ours for a couple of years and taken them on every cycle touring trip we've been on in that time. In the photo below we have two 4 litre water bladders strapped onto our rear rack.
Being lightweight and easily foldable (except for the black plastic cap) the bags can be packed away when not needed, ready to be filled with water at the next stop.
Another great feature of the bladders is the strap on each end which can be used for attachment to panniers, hooks, racks or whatever is handy. We have used the straps to hang the bladders up for easy use at the end of the day, as well as hooking them onto the bike rack for travel.
Our Salsa Powderkeg tandem often gets used as a water stand when touring. You can see the bladder hanging off the stoker's handlebars (rear) in the photo below.
We have the Ortlieb water bladders in store. They come in 2L, 4L and 10L sizing and typically come in black and blue. We can't see any point in carting water around in our tropical weather in black water bags, but...each to their own! Saves getting out the Trangia or Jetboil when you want that cup of tea!