Ventilated Stack Systems ~ where the layout of sanitary
appliances is such that they do not conform to the requirements
for the single stack system shown on page 781 ventilating pipes
will be required to maintain the water seals in the traps. Three
methods are available to overcome the problem, namely a fully
ventilated system, a ventilated stack system and a modified single
stack system which can be applied over any number of storeys.Ventilated Stack Discharge Systems