The following diploma exit project deals with extraneous water in sewer systems. The project is two-part and consists of a literature study and a data processing section. In addition, the project contains an annex section.

In the literature study, it has been found that extraneous water is a major problem in several supplies around Denmark. Of the supplies examined, extraneous water accounts for 24% up to 65% of the annual. The main reason for extraneous water is seepage, but also mismatches in separate sewer systems can give rise to a significant proportion of the unauthorized water. The supplies find that 2% to 10% of all separate sewered properties are mismatched.

Through the data processing section, it has been found that extraneous water in Grindsted, Aalborg Municipality, constitutes for between 46% and 64% of the total pumped volumes for the years 2015-2018.

In connection with the dimensioning of the new wastewater system to the city, it has been found that mismatches can have great significance for the capacity of the wastewater system. At the same time, the study shows that even small proportion of mismatches can improve the system's self-cleaning ability. Therefore, it is considered that the amount of mismatches should be kept to a minimum, but little amounts of extraneous water in the system can improve certain operating conditions.