Abstract: An improved chemical treatment system for hemodialysis machines, which includes a first three way valve which has a normally open position in the dialysis and rinsing modes of the hemodialysis machine. The valve in the normally open position couples a source of water through the valve to the bicarbonate pump for rinsing purposes before and after dialysis and the chemical treatment modes of the hemodialysis machine. In the chemical treatment mode of the hemodialysis machine the valve is switched to couple a source of treatment chemical through the valve to the bicarbonate pump. The chemical treatment system includes a second valve, which if in the normally open position, then only the bicarbonate portion and associated downstream portions will be chemically treated. In the closed position, the chemical will be switched to also flow through the whole hemodialysis machine from the water inlet to provide for a half or total system chemical treatment cycle.