On Tap: With David Bellamy, Vanessa Feltz, Sally Gray, Sue Lawley. Sue Lawley drives a tanker truck full of drinking water from the Thames Water region to South West Water region where it is twice the price. Peter Snow looks at Britian’s weather and how that effects water supply. Sally Gray and Janice Robinson compare designer bottled water with tap water. Vanessa Feltz goes under ground in the West End of London looking a restaurant waste clogging up the sewer system. And David Bellamy attempt to sell tomato’s grown in sewage.