Finally we have our own designed aerated bottom drain. The air enters through a 1.5 inch pipe, the air is then transferred, under the bottom drain, through the up right stem, and into the diffuser. This deletes any need for internal connections inside the drain. The drain comes complete with the adaptor to connect 1.5inch pipework to 3/8 inch or 8-10mm airline. ( This should be connected above water level, where we usually add two 90s, so the connector faces downwards, to avoid bending the airline. This model is the eco one, and the aerator takes a maximum of 40 litre air pump.