We are planning to relocate the existing kitchen as part of a large scale remodel/addition and DH and I are concerned about kitchen sink drain line placement in regards to the main septic drain located in the basement. This photo shows (in the green) circle where the main septic drain is located and where the proposed kitchen will be. The kitchen area is currently a carport but will be dug out and crawlspaced so flooring joists can run either direction. The existing house's joists run east to west. Our kitchen sink options are, in order of preference:

1) South wall centered approximately on the 16' wall.

2) West wall centered

3) Island area centered

With 1/4" drop per foot, the goal would be to get the drain line to the rear exterior wall as quickly as possible so the drain line falls along the wall instead of falling across the main walking area of the basement. My rough guesstimate has a fall of 18" from sink to drain line. Is that doable? Is it trouble waiting to happen, especially with two turns? Is their a pump type system that we could use to move the water/waste along? Am I crazy for even being concerned? TIA!