Collecting a sample from an open well: . Tie a sterile sample bottle on to a weighted length of rope; attach ½ Kg weighing stone as a weight below the bottle. . Remove the cap from the bottle septically and lower the bottle into the well to a depth of one meter. . Raise the bottle out of the well when no more bubbles raise to the surface. . Replace the bottle cap and label the bottle.
Transport of water sample Water sample should be placed in an insulated cold box immediately after collection, and should be processed with in six hours of collection.
Frequency of sampling
Multiple tube technique for counting fecal coliforms A 100 ml water sample is distributed (five 10 ml amounts and one 50 ml amount) in bottles of sterile selective culture broth containing lactose and an indicator. After incubation, count the number of bottles in which lactose fermentation with acid and gas production has occurred. Estimate the most probable number of coliforms in the 100 ml water by referring to probability tables.