Establishing the volume and velocity of flow-in drain and sewer systems at different times; in particular, focusing on peak flows normally associated with extreme weather events. This information is vital for both design (current hydraulic capacity: adequate, too low, over-sized?) and for repair installation consideration.
Should there be problems with corrosion, mortar or other degradation, it is necessary to know the nature of the effluent the pipe is carrying. This will include PH level, temperature and chemical composition e.g. issues such as high calcium or corrosive dissolved substances. A sampling pattern is needed to capture the range of effluents.