Pollutant quantification offers a wide range of applications in the field of water resources. With respect to sewage, a key issue is sample representativeness, as samples are often collected under technically challenging conditions. A new series of experimental measurements were conducted in actual sewers in order to investigate the influence of the major factors affecting sampling. Such factors include water velocity, sampling velocity, sampling tube location and orientation of the sampling point relative to the flow direction. Results show that the influence of these factors remains within 5% of the mass of the total suspended solids concentrations, meaning that in most practical applications, this influence may be neglected.