Selgas
Not al all sure I fully inderstand your original question however I will endeavour to assist you with the following ::: AS/NZ 3500 Part 2.2 Clause 3.9.1(b) states amoungst other things… In a non boundary trap area a minimum of 50mm vent is required to be provided at the upstream end on the drain, between the last and the second last fixture, but no further than 10 metres from the end of the main vented drain, or in the case of a gully installed on the main drain the distance from the gully to the vent should be no further than 10 metres.
