To clean out a floor drain, remove the strainer or grating covering the opening. Dig out the dirt and grease with a spoon or a stick. Clean out the bend or trap with a hooked wire or coil spring-steel auger. Check to find out whether a removable clean-out plug has been provided to make this job easier.
When the clogging material has been removed from the trap, pour a pail or two of hot water into the drain to wash out any loose material. Check the strainer itself and clean it with hot water and soap in order to open all holes. The floor drain should be checked regularly, especially one that is not often used, since water in the trap may evaporate. This would allow sewer gases to enter the room. Pour a pail of water into the drain periodically in order to make sure of a proper water seal.