Why a Detailed Water Loss Analysis Matters for Rural Communities

What is a detailed water loss analysis?

It is a desk audit followed by field checks. EPA's fact sheet on water audits and water loss control (July 2013) starts with a top-down audit: water put into the system over a year, minus authorized use, billed and unbilled, equals water losses.

The top-down audit uses records you already have, so EPA also calls it a desktop or paper audit. It often shows that some numbers are rough guesses. That is the signal to go further.

In our own experience, the gap is common. When MES interviewed 14 water providers in Colorado and Texas, half were dealing with water losses they had not identified.

A bottom-up audit checks individual parts of the system. EPA describes field methods such as:

• reviewing billing records for sudden changes in use at one location
• flow monitoring with customer meter records, metered districts or temporary clamp-on meters
• leak detection equipment, such as acoustic, thermal, electromagnetic or tracer methods
• condition assessment of mains, from visual checks to camera inspection and pipe testing
• hydraulic models calibrated to field data

EPA notes that bottom-up work costs more because it takes more staff time. The desk audit tells you where to spend it.

Why split real losses from apparent losses?

Because each one has a different fix and a different cost. In EPA's terms, real losses are physical: leakage from transmission and distribution mains, leaks and overflows at storage tanks, and leaks on service connections up to and including the meter.

Apparent losses are water that was used but not counted: unauthorized use, customer meter inaccuracy, and data handling errors in meter reading and billing.

Real losses cost you the energy and chemicals spent treating water nobody used. Apparent losses cost you revenue. A new meter program will not stop a leaking main, and a leak crew will not fix a billing system that misreads meters.

EPA also stresses metering at both ends. Source meters and customer meters are what make an accurate audit possible, and an unmetered system needs some metering before it can track losses at all.

How much water does a typical system lose?

EPA puts the average at 16 percent, and says up to 75 percent of that is recoverable. The fact sheet takes those figures from the Water Loss Control Manual (Thornton, Sturm and Kunkel, 2nd edition, 2008). Your system can sit well above or below that average.

One result from our own work: a Colorado water system MES worked with brought its water loss from over 30 percent to under 7 percent over four years, with new meters and replacement of old mains. That is one system's result, not a benchmark.

The order of work mattered. The first two years went to new meters, moved closer to the road, and smart metering that flagged service line leaks. The next two went to replacing mains, starting where they served the most users. The field work also found a small break at the system's best well that had cut its output, so check wells and raw water lines, not just distribution mains.

Texas sets its loss thresholds per connection, not as a percentage. TWDB's water loss audit rules, 31 TAC §§358.10 to 358.15, replaced the earlier water loss audit rule in August 2026.

The real loss threshold is 30 gallons per connection per day where a system has 32 or more connections per mile, and 57 gallons where it has fewer (§358.13). Apparent loss is measured against an allowed figure calculated for each utility.

What does Texas require of a small utility?

A water loss audit filed with the Texas Water Development Board, on a set schedule. Under §358.11, a retail public utility files every year if it has more than 3,300 connections or an outstanding TWDB loan, loan forgiveness agreement or grant. Smaller systems without board assistance file every five years.

Audits are due May 1. The person doing the audit must have completed TWDB's free water loss audit training. TWDB's water loss page says the most recent five-year round was due May 1, 2026, for the 2025 audit year.

A utility that files annually because it has TWDB assistance, or that is applying for assistance, must have its latest audit validated within 180 days of filing, or before TWDB considers its funding request if that comes first (§358.12). Validation checks the audit inputs and the uncertainty in them. TWDB staff can validate it, or a separately trained and certified validator can.

TWDB also offers technical help with audits (§358.14). Its water loss page also has a form to borrow TWDB leak detection equipment.

What does Colorado expect?

Colorado's rules center on larger providers, and its free water loss help is open to systems of any size. The Colorado Water Conservation Board's urban water efficiency page says covered entities, retail providers selling 2,000 acre-feet or more a year, need a state-approved water efficiency plan. They also report water use and conservation data each year under the HB10-1051 process.

For systems of any size, the Colorado Water Loss Initiative offers free training and technical assistance on the AWWA M36 audit method and Level 1 validation. The board notes these practices may be relevant to future permit and funding applications.

Our page on water loss work for Colorado distribution systems describes how we approach it there.

How does the analysis feed a funding application?

In Texas, it is a gate. Under §358.11(c), a utility that fails to file an audit, or to correct an incomplete one, cannot get TWDB financial assistance for water supply projects until a complete audit is accepted.

If real or apparent loss meets or exceeds the utility's threshold, part of any TWDB assistance for a water supply project must go to reducing the loss, unless the board grants a waiver (§358.13(b)). The rules list a detailed water loss assessment among the ways to do that, along with pipe or meter replacement and better monitoring (§358.10).

It also builds the project list. A ranked list of losses by type and location tells a funder what the money fixes. TWDB's Drinking Water State Revolving Fund lists correcting water loss deficiencies among the problems it finances.

This post goes deeper than the audit section of our guide to a better community water and sewer system.

Is your system ready for a detailed water loss analysis?

Answer yes or no. If you answer no to two or more, fix the data first.

1. Do you have 12 months of source-meter readings for the same period as your billing data?
2. Do you know when your source meters were last tested or calibrated?
3. Can you separate billed, unbilled metered and unbilled unmetered use?
4. Is your last TWDB audit filed, or in Colorado, have you completed a water balance?
5. Do you have a current map of mains, valves and service lines?
6. Do you log main breaks and leak repairs with dates and locations?

Then ask your engineer three questions. Which losses are real and which are on paper? Where should field work start? Which fixes belong in the next funding application? We work through these with utilities and municipalities in Texas and Colorado.

A note on limits: this is general education from EPA, TWDB and Colorado Water Conservation Board sources as of October 2026. Texas and Colorado rules apply only in those states, and your engineer and the agency have the final word.

Frequently asked questions

What is the difference between a water audit and a water loss analysis?

The audit is the accounting: water in, water used, water lost. The detailed analysis tests that accounting in the field, splits the loss into its parts and points to where each part happens.

Who can perform a Texas water loss audit?

A person who has completed TWDB's water loss audit training. Validation, where required, is done by TWDB staff or by a separate person trained and certified to validate.

I manage a rural water supply corporation in Texas with under 3,300 connections and no TWDB loan. Do we file every year?

No. Under §358.11, you file every five years by May 1, and the next round is due May 1, 2031. That changes to every year once you have an outstanding TWDB loan, loan forgiveness agreement or grant.

I'm the operator for a small Colorado water district, and our board thinks our meters are the problem. How do we test that before buying new ones?

Start with a water balance and check source meter accuracy, then test a sample of customer meters and review billing data. If apparent losses turn out small, most of the loss is real loss from mains, tanks or service lines. The Colorado Water Loss Initiative offers free help with this.

Related resources

• Addressing Small System Challenges with Water and Wastewater Experts | WEFTEC SERIES 2 | EP 1
• The Importance of Detailed Water Loss Analysis | EP 9
• Water and Sewer Funding: Is Your Community Eligible?
• Optimizing Small Water Treatment Plants Tips and Tricks for Rural Providers

Losing water and not sure where it goes?

Send us your last audit, a year of source and billing data and your system map. We will help you separate real losses from paper losses and rank the fixes.

We specialize in:

• Water loss and condition studies
• Water distribution system design
• Capital improvement planning for small utilities
• Funding applications and engineering reports
• Construction administration

Modern Engineering Solutions, McKinney, Texas. Contact: (214) 833-6748 or mod-eng.com