A dialysis system comprising: a sorbent cartridge including a zirconium phosphate layer followed by at least one of a urease layer, a zirconium oxide layer, or a carbon layer; a pump in fluid communication sorbent cartridge; and a control unit in operable communication with the pump, wherein the control unit is programmed to cause the pump to pump a dialysis fluid to flow (i) in a first direction through the sorbent cartridge, wherein the zirconium phosphate layer is contacted by the dialysis fluid before the at least one of the urease layer, zirconium oxide layer or carbon layer and (ii) in a second direction through the sorbent cartridge wherein the at least one of the urease layer, zirconium oxide layer or carbon layer is contacted by the dialysis fluid before the zirconium phosphate layer.