Louisville Water has completed its first large-scale inspection of a 48-inch cast iron transmission main while it was filled with water and in service. Louisville Water partnered with Pure Technologies for a condition assessment that covered 4.5 miles of the transmission main.

The inspection tool is called “Sahara,” an acoustic sensor that uses the flow of water to move it through the pipe while listening for potential leaks. This application of the Sahara tool also included an HD video camera and a Pipe Wall Analysis (PWA) tool. One of the unique aspects of the inspection is that the water main is filled and in service while the tool moves through the pipe, meaning Louisville Water did not have to empty millions of gallons of water and impact water service for thousands of customers. This inspection allowed Louisville Water to identify potential problems with the main and address them before the pipe fails.

 

How it works
To prepare for the inspection, crews installed 15 access points along the length of the water main. The Sahara tool was inserted into the pipe under pressure through one of the access points. A small parachute used the flow of water to pull the sensor through the water main while it was tethered by a steel cable. Once the inspection was completed, crews retrieved the tool by rewinding the cable. Depending on water flow, the Sahara can move up to 3 feet per second, and has a range of 1,500 feet or more. It took a little more than two weeks to complete the inspection of all 4.5 miles. There was no interruption to water service.

During the inspection, technicians from Pure Technologies and Louisville Water monitored the progress of the Sahara tool by watching its movement on a computer screen and listening for water leaks as small as a pin-hole. While the device provided real-time leak data, Pure Technologies’ technicians will analyze the pipe wall analysis data.

Inspecting gigantic water mains
Louisville Water has more than 4,200 miles of water main in its system. About 200 miles are pipes larger than 20 inches in diameter (transmission mains). The remainder is distribution mains, 16 inches and smaller in diameter.

In the 1980s, Louisville Water began a defined program to inspect, repair and/or replace the smaller water mains in the distribution system. It’s an aggressive approach to maintain the infrastructure. To date, Louisville Water has invested more than $160 million to maintain the distribution water mains. Engineers estimate the program eliminated nearly 7,300 water main breaks in a 20-year period.

Technology to inspect larger water mains — those larger than 24 inches in diameter — is still developing. In 2009, Louisville Water performed its first inspection of a large transmission main, a 48-inch main made of pre-stressed concrete. An inspection of a 60-inch pre-stressed concrete main followed in 2011, and an inspection of a 24-inch main in 2013. The water main in the Sahara inspection is made of cast iron, and it’s the first time Louisville Water has been able to inspect this type of water main as the technology was recently refined for this type of pipe.

Louisville Water has a long-term program to assess all 200 miles of transmission mains in the system allocating $4 to $5 million annually. Since beginning the transmission main assessment in 2009, Louisville Water has identified and repaired more than 20 potential problems with the larger water mains.

The 48-inch cast iron water main – nearly 100 years of history
The cast iron water main involved in the Sahara inspection was installed as unlined cast iron in sections beginning in the 1920s. Louisville Water began operations in 1860, and by the beginning of the 20th Century, the water company was starting to grow. This 48-inch main provided a larger and more reliable supply of water. In the 1990s, Louisville Water cleaned and lined the main. The company began planning the assessment last fall as part of its 2014 capital budget. In April, the water main had a large break at Eastern Parkway and Baxter Avenue. This water main also had two breaks in 2011.

Louisville Water engineers will use the data from the Sahara assessment to repair leaks and to determine if additional maintenance work is needed on the transmission water main.

About Louisville Water
Louisville Water began operations in October 1860 as Kentucky’s first public water provider and today provides an abundant, safe supply of drinking water to more than 850,000 people in Louisville Metro and surrounding counties. On average, the company produces 118 million gallons of Louisville pure tap each day. Louisville Water is recognized for its quality and innovation; in 2013, Louisville pure tap was named the “People’s Choice for Best-Tasting Tap Water in North America” by the American Water Works Association.