A renal therapy blood cleansing system is provided. The renal therapy blood cleansing system includes a blood filtering device in fluid communication with a blood circuit, a balance chamber configured to exchange like volumes of fresh and used therapy fluid with the blood filtering device, a first pump configured to pump fresh fluid to the balance chamber, a second pump positioned and arranged to receive used fluid from the blood filtering device, and a control scheme. The control scheme is programmed to isolate the blood filtering device from the second pump and deliver a volume of fresh fluid to the blood filtering device via the balance chamber while the second pump is isolated from the blood filtering device, so as to increase fluid volume within the blood circuit.