Figure 17 A river meanders its way down the left hand side of the diagram. A tube goes to the right from the river. The left hand end of the tube is labelled 'inlet screen'. The tube leads to a larger area labelled 'preliminary settlement tank or storage reservoir'. From here a tube goes to the right, then up, then right again. An arrow labelled '(1) chemicals added' points to this tube.
The tube turns down, and there is a cross. A vertical line goes up from the cross to a grey square. Above the square it says '(2) mixer'.
The tube now goes horizontally to the right where it joins a larger horizontal tank, which has two vertical divisions towards the left hand end. Each of these divisions contains a cross, and from each cross a vertical line goes up to a grey square. Above these it says '(3) flocculation tank'.
There is a '(4)' above the right hand half of the large tank, which is labelled 'sedimentation tank'. A tube labelled 'sludge removal' comes out the bottom of the tank, while from the right hand side another tube goes first right, then up, then right again, to a box labelled '(5) filtration'.
A further pipe leads to the right to another wider box, labelled '(6) chlorination'. From the right hand side of this box, a tube labelled 'to distribution network' goes to the right.
The river is coloured dark blue and as we move to the right across the diagram this lightens as we pass through each section.