(1)
Except as provided in Sentences (2) and (3), the minimum nominal pipe size of the vent pipe for a sewage sump or neutralizing or dilution tank shall be one NPS smaller than the NPS of the largest branch or fixture drain draining to the sump.
(2)
The nominal pipe size of every vent pipe for a sewage sump or neutralizing or dilution tank shall be not less than NPS 2, but need not be greater than NPS 4.
(3)
The nominal pipe size of a vent pipe for a macerating toilet system with a sump shall be not less than NPS 1½.