Packing it away again is a another story, set for a later post)!
The hanging black plastic bag holds 20 litres of water. In ideal weather, the water is solar-heated by laying the bag in the sun for several hours. We had bought the bag for our Kwiambal trip in January 2010 but only used it a few times there - and not since.
Given the lack of sunshine on this occasion (and Erin's keeness for a shower sooner rather than later), Nick and I used a billy of water from the fire to mix with other cold water.
Erin later reported the water temperature was too hot but she "managed"!