The accumulation of microorganisms embedded in biofilm within the drainage pipework leading from individual dialysis monitors in a renal dialysis centre, represents a significant threat to the safe operation of the whole centre due to blockage of the pipes and overflow of waste water. Attempts to disperse the growth with chemicals and disinfectants have been unsuccessful. Only mechanical rodding has removed the deposit, and regrowth has occurred. Those planning new dialysis centres should ensure that effluent pipework is readily accessible with multiple rodding eyes and is made of material able to withstand rodding and chemicals.