Note all the floor staining in the vicinity of the drain. This is a major red flag for an inspector and indicates substantial back-up or reverse flow out of the drain. There are various reasons for the localized flooding. Some common causes are:
- The storm-water system may have backed-up into the house during a major rain event.
- A major plumbing failure may have occurred in the mechanical room
- The floor drain may be plugged with debris. Then any normal drainage, off the air conditioning for example, will create a flooded floor drain.
For any prospective buyer, this condition should be identified and the implications discussed. In this case there is the potential for localized flooding in the basement which may create a electrical safety hazard (electrocution) as well as damage to floor finishes and wall structures.
If the drain is not flooding during the inspection to determine cause, then further review by a qualified plumbing contractor is essential.
Where the homeowner is concerned about future floor drain back-up and ponding, a useful device to have in any mechanical room is a wi-fi enabled leak detector, complete with alarm function.