Experimental study on meter registration accuracy at low flow rates and benefits of UFR implementation

Abstract

A water meter is a device used to measure the volume of water usage. It is generally used at each residential and commercial building in a public water supply system. Water meters typically measure and display total usage on a mechanical or electronic register. In most countries, water utilities install and maintain water meters primarily to monitor customer water use and have volume based pricing. However, like other mechanical devices and based on the meter’s metrological characteristic, they have difficulty in measuring very low flow rates mainly between 1 L/hr to 15 L/hr. Moreover, after a few years of use, water meters become less accurate (i.e. under and over registered flow) and also the minimum flow registration level of the meter will increase, thereby resulting in higher volumes of unaccounted for water. Such non- or under-registration of low flow rates is one of the main reasons for apparent water losses and represents lost water revenue to the water business; for a city with a fleet of aged water meters, the average starting measurement threshold is higher resulting in higher water losses. Lost revenue is not the only concern but wasted natural water resources that are difficult to replace. The level of non- and under-registration of a fleet of in-situ water meters in a typical city is still largely unknown. This trial study is an attempt to understand low flow rate registration levels before and after the implementation of an intervention (i.e. Unmeasured-Flow Reducer (UFR)). The UFR is designed to reduce the amount of water that flows below the flow meter measurement threshold by changing the flow regime through the water meter at low flow rates. The results from this study feed into the greater study attempting to estimate the level non-registration of domestic water.