Abstract: Hemoglobin or hemolysate is used as an indicator for leakage detection in the dialysis membrane interface separating the sterile from the nonsterile circuitry in a recirculating peritoneal dialysis system. The indicator is dissolved in the steril dialysis fluid and is retained within the sterile circuit unless leakage occurs in the membrane. Upon rupture or other leakage in the membrane, fluid turbulance and pressure gradient cause crossflow between the sterile and nonsterile circuitry, endangering the patient with infection, peritonitis and endotoxin shock. Such crossflow is detected by the concurrent coloration caused by the mixing of hemoglobin indicator in the nosterile dialysis fluid.