Two pipe system of providing building drainage consist of

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Detailed Solution:

in two pipe system two sets of vertical pipes are laid ie one for draining night soil and the other for drainage sullage

the pipes of first set carrying night soil are call soil pipes and the pipes of second set carrying sullage from baths are called sullage pipes or waste pipes. 

The soil pipes and the waste pipes are seperately ventilated by providing ventilation pipes or antisiphonage pipes