When the water system is below the pipe to the septic system, you need to make the shit flow up hill, counter to the laws of physics.
How do you do that?
Well you do it with a pump which is inside a septic basin below your basement floor, and thus below the source -- all the showers, sinks and toilets in the basement. This pump chews up all the 'lumps' and pumps them up wards and in to the pipe to the septic system.
The Check Valve: Stopping the Shit from rolling down hill
A key element of this system is the check valve shown in the picture to the right. A check value only allows the fluid, and the 'crap' it contains to only flow one direction. When the pump stops any material in the pipe above the check valve stays above the valve, and does not flow back into the septic basin.
That's how you make shit flow up hill, and stay there!
Related Posts:
installing the septic system - status
installing a shower: part 1
installing a toilet: part 1
;-)