Abstract: An arrangement in vertical sewage system pipes for preventing rodents, such as rats, from entering dwellings, living accommodation, office accommodation, and similar building structures. The arrangement includes a frame which is L-shaped in cross-section with an outwardly extending flange sealingly inserted in a joint between two mutually adjacent pipe sections and an axially extending flange to which are attached a plurality of springing wires or rods so as to form a wire cone which tapers in the direction of sewage flow. The springing wires or rods terminate at the apex of the cone in anear touching relationship. The wires or rods are made of stainless steel with a wire gauge of from 0.7 to 2.5 mm or of fiber glass with a wire gauge of from 0.8 to 2.0 mm.