14-04 Wet venting and offset

Question: 14-04Code Section: 7Date: 10 February 2014OBC 2012 Reference:

Question Submitted: Sentence seems to be in conflict with the Appendix illustration A-89. The wording in the sentence makes no reference to “no connection to the offset” as indicated in the illustration. In checking the NPC, it does not refer to this either.

1) Is the illustration correct and enforceable?
2) Should there be a clause (iii) added to to restrict a connection to the horizontal offset, thus making the illustration to coincide with the wording?


 (1) The appendix is not an enforceable section of the OBC, it is only provided for examples to assist in clarifying the prescriptive requirements. The illustration is not incorrect by the wording of no connections allowed, as in this instance there is no length assigned to the offset. There could be times where it would be permissible for connections. The drawing shows that the wet vent portion is more than 2 storeys with a total of 10 FU’s load on the wet vent. According to Table the wet vent size would be 4” since 2 W.C.’s are in the group, which allows the max. offset to be 2.5m. explains when dealing with connections of a waste pipe to a nominally horizontal waste pipe (which according to definitions, a wet vent is) the connection shall be min. 1.5m from the vertical section. Therefore there could be a connection in this illustration if the offset is more than 1.5m in length and the connection location is made properly.

(2) If it is felt there is a need for not allowing connections to the offset, then yes, item (iii) should be added through a request to the MMAH for a code change.