Different methods are used to collect water samples; techniques include dip samples, direct method samples, discrete depth samples and peristaltic pump samples. Of these the simplest and most common is the dip sample, in which the sample container is dipped into the water.
Although surface sampling can be used to test for concentrations of many different pollutants and water characterization parameters, the ones usually tested for are biochemical oxygen demand (BOD), dissolved oxygen (DO), temperature, acidity (pH), turbidity, phosphorus, nitrates, total solids, conductivity, total alkalinity and fecal bacteria.
When sampling, a clean container must be used for accurate results. For most samples, the container should be cleaned with phosphate-free soap and then rinsed three times with tap water, followed by a rinse with deionized water. For nitrate and phosphorus samples, rinse the bottle three times with tap water, then once with 10 percent hydrochloric acid, and three times with deionized water.