Basement floor drains
How does a basement floor drain/trap work? If the basement is dry, doesn't the water in the trap eventually evaporate and expose the basement to sewer gas? If there is water visible in the bottom of the drain, does it indicate that there was a backup of some sort recently? Thanks!
Unless water is added to the drain, then it will dry out and allow fumes into the basement, assuming it is connected to the sewer and not to a sump pump pit. Water in the trap does not have any real indication. It could be water that has not evaporated yet, or it could be that the drain is connected to the side of the main drain and some water backflows during heavy usage such as a toilet or washing machine draining.