Water Audit, SCCRWA

South Central Connecticut Regional Water Authority (SCCRWA)

Water_meterA water audit was conducted according to the guidelines outlined by the American Water Works Association (AWWA) in Water Audits and Loss Control Programs, Manual of Water Supply Practices – M36, Third Edition. The data reviewed and analyzed included the volume pumped for each source, source meter errors/calibration, the volume of water imported/exported, billed and unbilled consumption, recorded leakage, main breaks, and unauthorized consumption. Key performance indicators, including Infrastructure Leakage Index (ILI) and non-revenue water, were evaluated to track management of the water utility.  Based on the results of the audit, recommendations were made to improve system operation and reduce non-revenue water.  Although the RWA’s non-revenue water water rate was around 15%, the audit confirmed that the RWA’s Infrastructure Leakage Index or ILI was at industry best practice levels, confirming that apparent losses made up the majority of RWA’s water loss.

The recommendations in the audit report included verification of flows at ten production meters, where serious over-reporting of flow was identified.  As a result of this work, two of the production meters were replaced in 2013, including a 54-inch diameter venturi tube at the RWA’s main source.  The audit report also confirmed statistical analysis of customer meter testing that led to a decision to focus meter replacement work on piston-type meters while leaving older but more statistically accurate nutating disc-type meters in service for longer periods.

Condition Assessment of Cast Iron Water Main Samples

Pipe_Crush_TestAdvanced condition assessment of cast iron water main samples and water infrastructure provides insight into the quality and reliability of a water distribution system. The goal is to be able to efficiently and effectively run the water distribution system by allocating capital to areas of the system that are in need of rehabilitation or replacement. Tata & Howard is a leader in condition assessment methods for water distribution system pipe assets.

In 2007, Tata & Howard began extracting one foot long cast iron water main samples ranging in diameter from 6 to 12 inches as part of a cleaning and cement lining water main rehabilitation project.  Since then, we have evaluated a significant number of cast iron water main samples for several water distribution systems throughout Massachusetts and Connecticut, typically during a rehabilitation project, water main failure, or water main replacement project.

Sections are evaluated using several criteria:

  1. Pipe Class Estimation Based on Remaining Wall Thickness
  2. Visual Inspection
  3. Pipe Crushing ANSI A21.6-13 Yields Break Load of Sample
    Samples are loaded, one at a time, onto a machine that monitors the application of load in pounds, and the load required to cause the main to break is then recorded. Additional visual inspections are also made and recorded.
  4. Remaining Factor of Safety Estimation

In the past, cast iron pipe manufacturers incorporated a 2.5 minimum factor of safety (FOS) to the crushing load necessary to break a water main.  The manufacturer’s FOS can be compared to the crushing load that was measured at the materials testing facility, which then yields the estimated remaining FOS of the water main sample.

Condition assessment is beneficial in assisting a utility in the decision to rehabilitate a water main or schedule it for replacement, and in identifying asset classes that are candidates for replacement.  The visual inspection provides an assessment of the quality of the water main, which assists in properly allocating capital funds to mains that are on the verge of failure or in need of rehabilitation.


Whitepaper:

Pipe condition assessment combined with break data for New England communities allows for continued analysis of problem pipes in distribution systems.  This whitepaper outlines the research completed and the data collected to help pinpoint the next problematic pipe cohort. Read the complete whitepaper by clicking below: