Water Loss Percentage

What is this formula?

Water Loss Percentage quantifies the fraction of supplied water that does not reach end users.

The indicator is widely used by water utilities and regulatory agencies to evaluate system performance, leakage control, infrastructure condition, and operational efficiency.

Water losses may include physical losses such as leaks and bursts, as well as apparent losses caused by metering inaccuracies or unauthorized consumption.

When to use it

Use this formula when evaluating:

- Municipal water distribution systems

- Leakage reduction programs

- Utility performance benchmarking

- Water conservation projects

- Infrastructure rehabilitation plans

- Non-revenue water assessments

Example

A water utility introduces 150,000 m³/day into its distribution network.

Customers receive 123,000 m³/day.

Data:

Ws = 150,000 m³/day

Wd = 123,000 m³/day

Formula:

WL = (Ws − Wd) / Ws

Substitution:

WL = (150,000 − 123,000) / 150,000

WL = 27,000 / 150,000

Result:

WL = 0.18

Water Loss Percentage = 18%

The distribution system loses approximately 18% of the supplied water.

Applications

- Water utility management

- Leakage monitoring

- Infrastructure planning

- Regulatory reporting

- Sustainability studies

- Water conservation initiatives

Note

This formula provides an overall estimate of water losses but does not distinguish between physical losses and apparent losses. Detailed water audits often separate these categories and may use more sophisticated methodologies recommended by organizations such as the International Water Association (IWA).