Water metering

Water metering is the process of measuring water use through water meters.

Prevalence
Water metering is common for residential and commercial drinking water supply in many countries, as well as for industrial self-supply with water. However, it is less common in irrigated agriculture, which is the major water user worldwide. Water metering is also uncommon for piped drinking water supply in rural areas and small towns, although there are examples of successful metering in rural areas in developing countries, such as in El Salvador.

Metering of water supplied by utilities to residential, commercial and industrial users is common in most developed countries, except for the United Kingdom where only about 25% of users are metered. In some developing countries metering is very high, such as in Chile where it stands at 96%, while in others it still remains low, such as in Argentina.

The share of residential water metering in selected cities in developing countries is as follows:


 * 99% in Santiago de Chile (1998)
 * 96% in Abidjan, Côte d'Ivoire (1987)
 * 62% in cities in Guatemala (2000)
 * 30% in Lima, Peru (1991)
 * 28% in Kathmandu, Nepal (2001)
 * 5% in Conakry, Guinea (1984)
 * 2% in Buenos Aires, Argentina (1992)

Benefits
The benefits of metering are that


 * in conjunction with volumetric pricing it provides an incentive for water conservation,
 * it helps to detect water leaks in the distribution network, thus providing a basis for the reduction of non-revenue water;
 * it is a precondition for quantity-targeting of water subsidies to the poor.

Costs
The costs of metering include


 * the investment costs to purchase and to install meters, as well as
 * the recurrent costs to read meters and to issue bills based on consumption instead of bills based on monthly flat fees.

While the cost of purchasing residential meters is low (in the range of US$20 per meter), the total life cycle costs of metering are higher. For example, retrofitting apartments in large buildings with meters for every apartment can involve major plumbing work and can be very costly.

Problems
Problems associated with metering arise particularly in the case of intermittent supply, which is common in many developing countries. Sudden changes in pressure can damage meters, so that many meters in cities in developing countries are not functional. Also, some types of meters become less accurate as they age and underregister consumption thus leading to lower revenues, unless they are being replaced regularly. Many types of meters also register air flows, which can lead to overregistration of consumption, especially in systems with intermittent supply, when water supply is re-established and the incoming water pushes air through the meters.

Effect on consumption
There is disagreement as to the effect of metering and water pricing on water consumption. There is evidence from the UK that there is an instant drop in consumption of some 10% when meters are being installed. The price elasticity of metered water demand varies greatly depending on local conditions. The effect of volumetric water pricing on consumption tends to be higher if the water bill represents a significant share in household expenditures.