Apparent losses and real losses are two main components of water losses in water supply systems (WSSs). Apparent losses are caused by water meter inaccuracies, illegal consumption, and data handling errors whereas real losses are associated with leakage, pipe bursts and overflow from storage tanks. In well managed WSSs, apparent losses mainly result from inaccuracies of water meters. Performance of water meters is affected from many factors such as meter type, class, size and age, installation, and water consumption profile. In this study, new and used multi-jet type water meters, which is one of the most widely installed water meter type, were tested under different flow rates in a laboratory setup for performance evaluation. Starting flow rates and metering errors of new and used multi-jet water meters under varying flow rates were tested. Average starting flow rate for the new multi-jet (MJ-N) water meters is determined as 7.02 l/h whereas the multi-jet water meters with an age of more than 9 years (MJ-3) old have the highest starting flow rate with an average value of 40.18 l/h. Meter degradation for average starting flow rates shows an almost linear trend. All tested water meters tend to make more measurement errors at lower flow rates. As measurement errors for ageing meters (MJ-2 and MJ-3) are similar at medium and high flow rates, ageing of meters cannot be described by linear degradation. This study showed that ageing and water consumption profiles have a great impact on water meter performance. An evaluation on ageing effects on the accuracy of water meters is provided in this study.