The Shell Water Detector is a device for determining the presence of finely dispersed undissolved water in jet fuels at concentrations lower than those normally detectable by visual examination. Water dispersions of this type can result from the emulsification of a water/fuel mixture during pumping or from precipitation of dissolved water due to a fail in fuel temperature.

The Shell Water Detector should be used as follows to check samples
 of jet fuels immediately after they are drawn.
a) Road vehicle and RTW drain samples - before discharge into airport storage.
b) Bottom samples from airport tanks - immediately before release.
c) Fueller and trailer compartment drain samples - after each replenishment.
d) Hydrant dispenser filter drain samples - after each aircraft fuelling.
e) Fueller filter drain samples - after
 the first aircraft fuelling, after filling or topping up either Fueller or trailer.
f) Drain samples from filtration equipment on  hydrant delivery and Refueller loading rack delivery