The City of Larvik has a customer base of 39,000 people. Larvik is also a holiday destination, and during summer of 2018, the municipal water treatment plants had difficulty meeting demand. Larvik has several pressure zones, altitudinous reservoirs and pumping stations. The distribution system has eight major districts, subdivided into 20 DMAs with 35 district meters. The city decided to implement KeyZones monitoring system that consists of intensive data collection and systematisation. Operational in 6 weeks, the system gathered smart meter data from the past 2 years to reference for initial analysis of the KPIs.

At the handover of the KeyZones system, initiatives and methods for active NRW optimisation were selected, based on the DMAs with the most potential for NRW-reduction. A 20-25 m³/h leak with six months runtime was found after a week. Another leak of 35-40 m³/h, with 5 months runtime was also identified. The investment costs for implementing KeyZones was, despite the low water price, recouped through the repair of those leaks. Further initiatives such as changes to pressure zones were implemented, enabling Larvik to reduce the ILI from 5.0 to 2.5, within 6 months.