In our house, we have a partially below grade basement. Occasionally, our basement will smell like sewer gas (farts) but I can not determine where the smell is coming from.
The basement does have sewer clean-out drain in the utility/washroom but our clean-out drain cap is securely tightened. It seems like the smell is coming from the downstairs bathroom which is next to the utility room.
The bathroom downstairs is hardly used but I occasionally flush the toilet and run the shower to keep water from evaporation from the P trap on the shower.
Additionally, it seems that when we use an upstairs bathroom the smell is more present.
Anyone have any ideas on how I can find the smell or what I can do to resolve the smell?