This paper presents the problem of sulphate corrosion in the sewage network systems. The sulphate corrosion and its consequences are presented. The issue of biological corrosion, sulphate reducing bacteria (SRB) and sulphur-oxidizing bacteria (SOB) as the two main groups of microorganisms participating in the process of sulphate corrosion is described. Subsequently hydrogen sulphide was characterised and stages of sulphate corrosion leading to the formation of ettringite (hydrous calcium aluminium sulfate) were presented. At the end a possible protection against the sulphate corrosion was outlined. It has been concluded that sulphate corrosion is a serious threat to the sewage network systems.