This P trap gully is used to prevent drain odours from escaping into the surrounding atmosphere. It is commonly found at the foot of a rainwater pipe.This gully has an access door for inspection and cleaning, and a fitting lug on the crown of the bend.¬As Halifax pipes and fittings have no sockets, couplers are required to connect this gully to another pipe or fitting. A full dimensional drawing of this product can be found in the  Halifax technical catalogue.