A vertical flow system comprises a flat level gravel bed topped with sharp sand and then planted with Phragmites. Some systems have a network of pipes with downward pointing holes and surrounded by large stone. This allows the effluent to seep into the pipe and drain out to the collector sump.
Dosage of the bed is periodic allowing previous dosing to percolate down through the rhizosphere.
It is vital that good coverage over the whole area of the bed is achieved for the system to function at its maximum.