Supplying treated greywater within buildings delivers continuous additional resilience and improvements in water efficiency. This includes the making available (by substitution) of greywater resources suitable for non-potable purposes such as flushing toilets. Thereby, the overall daily consumption of pristine potable water for flushing and other lower quality uses is reduced. The empirical measurement of turbidity was confirmed as an accurate and resilient indicator of greywater quality, greywater treatment process efficiency and of well-functioning greywater reuse systems in the short-, medium- and long-term. The methodology applies turbidity monitoring for evidential management and control of treated greywater quality, essential for greywater recycling in the building stock. The results demonstrated evidence of co-variation between turbidity and biochemical oxygen demand in a lightly-loaded greywater treatment process. Real-time monitoring of turbidity delivers responsive, reliable, in-situ and remote measurements for informing building management systems (BMS), comprising an essential part of routine monitoring of greywater treatment plant. The analytical evidence confirms the importance of turbidity measurement and control in both current and future UK and international greywater standards. By undertaking turbidity measurements in compliance with BS 8525-2:2011, greater assurance in the use and compliance of greywater supplies in the built environment is achieved. Consequently, the rationale for including the empirical measurement of turbidity to demonstrate satisfactory management of the greywater quality, treatment system operation, monitoring and compliance in buildings has been confirmed. (C) 2020 Published by Elsevier B.V. on behalf of Institution of Chemical Engineers.