We read with interest Cuadrado-Payan et al.’s letter on the potential environmental benefits of newer haemodialysis systems (NxStage System One®, Physidia S3®, Tablo®, DIMI®) compared with conventional machines. Because these devices are designed to operate at lower dialysate flows, we agree they can reduce dialysate use and associated water consumption. However, some systems–notably Physidia S3 and, in some configurations, NxStage–rely on packaged dialysate. Producing dialysate bags requires several litres of source water per litre of purified water, plus additional water for plastic manufacture.