A dialysis system is described. The system comprises a drain tube for carrying effluent dialysis fluid a drain container that is configured to receive the effluent dialysis fluid from the drain tube and a load cell (234). The drain container includes an at least semi-rigid body having a first key feature. The load cell includes a second, mating key feature (246) that is positioned and arranged to mate with the first key feature when the drain container is loaded onto the load cell.
