Sewage system odours inside can indicate a dry trap, cracked air vent

https://telegra.ph/From-Drips-to-Disasters-A-Geelong-Plumbing-professionals-Tips-for-Common-Family-Plumbing-Issues-04-18

Drain odours inside can show a completely dry trap, cracked vent, or partial clog; Geelong homes with large trees or older sewer lines may need CCTV evaluations to locate invasions and prevent persisting smells.