Water Loss Audit
Leak Detection | Water Loss Audit Resources | FAQs
Traditionally, the water utility industry has used percentages to determine water loss, but in order to more efficiently manage your utility you should be able to answer several questions:
- Where did we lose the water?
- How much water was lost, expressed as a volume?
- How much did the loss cost the utility?
- Why did we lose the water?
The Texas Water Development Board utilizes a methodology derived from the American Water Works Association (AWWA) and the International Water Association (IWA). This new standard uses terminology such as authorized consumption, real loss, apparent loss, and non-revenue water.
Authorized consumption is water the utility gave someone permission or authorization to use. Whether it was billed or not, it is still authorized consumption.
We now use the terms Real Loss (water lost through distribution system leakage and excessive pressure), and Apparent Loss (includes water that was not read accurately by a meter, unauthorized consumption, including water taken by theft, data analysis errors and data used for billing). Since real loss is water lost while in the distribution system, a production cost is associated with it. The retail rate is associated with the cost of apparent loss because it had the opportunity to be metered.
Non-revenue water (NRW) is simply water that the utility does not receive compensation for. For clarification purposes NRW consists of the unbilled categories of authorized consumption and both apparent and real loss.
The Water Audit Worksheet is a "top down" audit and is referred to as a "desktop" exercise using existing estimations and records. If the utility desires to become more efficient, the next step in this process is the "bottom up" audit, which involves a detailed investigation into actual policies and practices of the utility. It should be phased in only after the utility staff has a thorough understanding of a "top down" audit and the IWA methodology, terms, and procedures.
For further explanation of this methodology and for detail definitions please review the Water Loss Manual.
Water Loss Audit Worksheet
The TWDB now provides a secure website to ensure the security of the data provided by water utilities all over Texas. To access the Water Loss Audit Worksheet online you must first register by creating a username and password. The New User link will direct you to that page. Once you have created a username and password, you may use the Registered User link to request access to a particular utility. Once access is approved by TWDB staff you will receive a confirmation by email granting access.
Water Audit Worksheet Resources
- Water Audit Worksheet Instructions
- Assessment Scale (Appendix 1.3)
For further information or questions, please contact conservation staff.