Tanzanian villagers have begun using an energy-saving method to sterilise their drinking water - leaving the water under the sun. The piped water supply to Ndolela village in the central Iringa region is intermittent and even when it does it flow, it is not clean enough to drink. When the pipes run dry, villagers get water from a dirty spring. Mother of five Rose Longwa says the new process has changed her life. "We no longer suffer from stomach illness. That's because the water is clean and safe."