Gully Traps, Floor Traps & Yard Gullies
A gully collects surface water or waste discharge at ground or floor level and passes it into the underground drain, holding a water seal so that drain air cannot escape at the opening. In the UAE the same fitting is commonly called a floor trap indoors and a gully trap or yard gully outside.
Also searched as: gully trap, gulley trap, floor trap, yard gully, bottle gully, hopper, road gully, point drain
Trapped and untrapped
A trapped gully holds a water seal and is used wherever the gully is open to a room, a yard or a walkway. An untrapped gully is used where the seal is provided elsewhere in the system, or on purely surface-water runs discharging to a soakaway or storm system where no foul air can be present.
Patterns
Bottle gully — a compact vertical body with a removable centre, easily rodded, used for rainwater downpipes and small yard areas. Yard gully — larger body with a grating for open external areas. Hopper — open funnel taking waste discharge above ground. Back-inlet gully — takes a waste or rainwater connection into the side of the body below the grating, so the incoming pipe is sealed rather than discharging over an open grate.
Gratings and covers
Gratings are supplied in plastic and in metal for higher duty. Choose the grating to suit the loading: pedestrian areas, light vehicular access and heavy vehicular access all have different requirements, and in the Gulf the grating also has to survive thermal cycling and UV. Rectangular and square gratings are available with the standard round bodies.
Seal depth and evaporation
Specify a deep seal on any gully in a location that will not see regular discharge. External gullies in an Abu Dhabi summer can lose a shallow seal to evaporation in a matter of days, after which the gully is simply an open hole into the drain.