These are systems where multiple independent pots are connected to a central nutrient reservoir. It is plumbed in either a ‘recirculating’ (Fig 1.4a) or ‘run-to-waste’ mode (Fig 1.4b) depending upon which medium is used. However, it is undesirable to have run-to-waste specific media (e.g. soil, coco fibre, Rockwool) in some pots and recirculating specific media (e.g. expanded clay, perlite) in others. This is because of the different feed frequencies and volumes required for each.