You might try listening and following the sound. Our water pump is located behind a panel in a cabinet located in the rear, L/H corner of the trailer. It is at floor level just inboard of the fresh water gravity fill port. Locate the fresh water fill - then look for a removable luan panel or look under/behind a drawer inside the trailer in that area. You might also do a forum search. There have been several threads about water pumps on various trailers.
If you provide the forum with the exact model of your trailer, someone with the same model might respond with the info - good luck
Sorry, John. You must have posted your answer while I was typing(two fingering) mine.