The 110mm Bottom drain is provided with an aerated dome for supplying the pond with air. 1 "M threaded connector to connect a flexible hose that is used to supply the air diffuser. The 110mm outlet can be adappted up to 4" pressure pipe (look at related products)that Allows the evacuation of the waste more efficiently than by pumping, The air fitting on the bottom of the sump can also be addapted to take pressure pipe, Thus the supply of air is not done by a hose, but rather by a pipe PVC pressure of 20 mm, much safer and strong.(look at related products for this item)