From 3" - 6" diameter 1/8th in per foot would be minimum BUT the average we try to use would be 1/4" per foot

From 3" - 6" 1/8th in per foot would be minimum 1/4" per foot is generally accepted as good pitch try not to exceed 1/2" per ft

To confirm, then over 24', I would need a slope of 6"? If I had one full bathroom and kitchen sink/dishwasher would I need a vent pipe to the roof for each drain location or only need one? If only one should I place it farthest away from the septic, closer to septic or in between?

Thanks,

Jim

Golker