Abstract
This study looks at the application of delayed action Passive Infrared (PIR) sensors in the control of water use for urinal flushing. In this we briefly review the literature on urinal controls before reviewing four different approaches to PIR urinal controls. Existing literature discusses some of the pros and cons of different types of urinal control. However, the literature does not consider the differences that occur within individual approaches, based on the way controls operate. This study was initiated at the University of Surrey during 2019 following a water saving audit, in an attempt to bring down one of their largest users of water. This paper therefore aims to identify the most effective way to reduce water consumption of urinal systems, through retro-fitting PIR control systems within the variety of settings across university campuses. This paper also reviews the different reductions achieved over periods of differing use, during term-time, holidays, COVID-19 lockdowns, and the 'new normal'. It found that grouped delayed action flushing was the most effective form of urinal control for reducing water use. It, achieved a 59-64% adjusted reduction during non-COVID-19 periods, and a 35% reduction against the control group during lockdowns saving 98,000 L/day on average across the study.