Who is Stealing Your Water? discusses the role of water theft in non-revenue water (NRW), with tips for its reduction through tamper-proof meters and effective Meter Data Management. In this blog we look at the impact of water meter inaccuracy on NRW.
In the Texas Best Management Practices Guidebook, “System Water Audit and Water Loss” the first recommendation for reducing NRW is to check customer meter inaccuracy due to meter wear, malfunction or inappropriate size or type of meter.
There are three main types of water meters:
- Mechanical – Flowing water rotate an impeller and measures its velocity or displaces a piston to calculate water volume.
- Ultrasonic – Use ultrasonic beams to assess the velocity of the flowing water.
- Electromagnetic – Use electromagnetic properties to determine the water flow velocity require a power input.
Customer, or residential, water meters typically comprise about 65% of the water meters deployed by a water utility. Since inaccurate meters tend to under-register water consumption, the cumulative effect of inaccurate meter readings at the residential level can be significant.
Water utilities can mitigate this issue in two ways:
(1) Choose the most suitable water meter
Taking into account the following considerations:
- The quality of the water: High levels of sediment in the water, for example, can cause considerable wear and tear on the moving parts of mechanical water meters.
- Flow variability: Mechanical water meters tend to work best with specific flow ranges. If there is considerable flow variability in the system, ultrasonic or electromagnetic water meters might be a better choice.
- Low flows: Many water meters have difficulty measuring low water flow – leading to under-registration of water consumption. If a system is subject to low flow levels, it’s very important to pick the right type of meter – such as an ultrasonic, or electromagnetic — and to make sure they are the right size.
(2) Replace water meters on a 10-year cycle
Since the accuracy of any meter will decrease over time.
If residential water meters comprise 65% of the meters deployed by a water utility, what about the other 35%, i.e., the bulk, or production, flow meters? Although bulk meters are not part of the billing system, they play an important role in measuring total system production, which is a critical input to calculating system NRW. And if NRW is not being calculated properly, it cannot be managed. As pointed out by Malcolm Farley et al in the The Manager’s Non Revenue Water Handbook (Ranhill Utilities Berhad and USAID), because the number of bulk meters in the system is relatively small, each one measures a greater proportion of the flow and an error on even one of these meters will skew the system metrics. It was with this in mind that The Arad Group developed Octave, its revolutionary ultrasonic bulk meter designed for exceptional precision, reliability and maintenance-free longevity.