For tracing the direction of flow or to where a drain pipe runs. The recommended dilution rate is one pot of dye (approx. 230g) to 9 litres of water. The liquid is then use at a rate of 140ml-250ml per 450 litres, depending on the ground conditions. One pot (approx. 230g) of drain dye will treat 28,800 litres at 140ml per 450 litres and up to 16,200 litres at 250ml per 450 litres. Fluoresces under black light. Does not require UV light.