If you run an 80 foot pipe, the slope will be 20 inches at 1/4 inch a foot. That is quite a slope (nearly 2 feet).

Are you sure your existing drain pipes are buried deep enough? Also you would have to use two inch pipe and possibly install a new clean-out or two for that pipe. Check with your local inspector to be sure.

It seems the pump would be the best route to follow in your situation. Pump the waste into the closest drain pipe.

: We have a rancher with a walkout basement and are on a septic tank. I am contemplating putting in another kitchen on the lower level and the sink will be at the opposite end of the house from the septic tank. The distance would be about 80 feet for the drain. I guess at about 1/4" drop per foot I might just make it but I wonder if there is an easier way?? The location of the new sink would be almost directly below the drain for the upstairs sink and I could quite easily tap into that but how could I get the water there? Are there pump systems available? Thanks for any help.