Reply To: to trap or not to trap…. Home › Forums › Public Forums › Drainage & Sewerage › to trap or not to trap…. › Reply To: to trap or not to trap…. 11 Dec 2002 at 11:10 pm #300124 Retired plbg1Participant It might run down to a floor drain below. It could be an indirect drain running into a untraped drain, put a trap in the line.