What's Up With all the Water Main Breaks in Atlanta?

There are approximately 2,800+ miles of water mains distributing water throughout Atlanta.  These water mains vary in both size and materials from which they were manufactured.  Old and new water main diameters range in size anywhere from 2 to 72 inches. Older water mains are manufactured from cast iron, while newer ones have been manufactured from ductile cast iron, concrete, or PVC.  However, since the water system in Atlanta dates back to 1875, more than 50% of the water mains in use were manufactured from cast iron. 

Cast iron is the root cause of most of the water main breaks in Atlanta. Traditional cast iron a very strong material, making it a good choice for water mains built more than 60 years ago, especially since there were no alternatives. However, cast iron is very brittle, tends to break when bent or twisted, is susceptible to rust and corrosion, and does not adjust well to rapid temperature changes. In the 1930's, manufacturers began lining the interior of cast iron water mains with a thin coat of concrete to reduce interior corrosion and improve flow rates and coating the exterior with tar to reduce exterior corrosion. However, even cast iron water mains  with these improvements have a useful life expectancy between 75 and 125 years.  

In older East Coast cities like Atlanta, there are hundreds of miles of cast iron water mains that have far outlived their useful life. In the 1960's, manufacturers began making water mains using ductile iron, which is far more flexible and bendable than plain cast iron. Since then, most new water mains are constructed of ductile iron and repairs of traditional cast iron are made with ductile iron. Starting in the 1990's, some new water mains were constructed from concrete or heavy duty PVC.  However, due to replacement costs and budgetary constraints, most of these cities, including Atlanta, appear to have adopted a "wait and see" attitude before repairing or replacing aging water mains constructed using cast iron.

In addition to being put into service beyond their useful life, there are a variety of factors that can contribute to failures within aging cast iron water mains.  Soil settlement can cause brittle cast iron water mains to bend and break, especially in areas with expansive soils which shrink/expand when subjected to fluctuations in the water table. Rapid pressure increases triggered by the failure of other water mains causing shutdowns and rerouted water flows can also cause aged cast iron water mains to fail. Rapid temperature changes in the water flowing through aged water mains is a less likely cause of failure, but is also a candidate to cause a failure. Finally, corrosion on either the interior or exterior of cast iron water mains can cause a reduction in wall thickness that then contributes to failures caused by soil settlement, as well as changes in pressure and temperature. 

In cities like Atlanta that have an aging water main infrastructure, residents should expect water main failures to both continue and increase over the coming years. Each water main break shuts down water supplies preventing residents from drinking, cooking, washing clothes, flushing toilets, bathing, and overall health care. Water main breaks impact health care facilities, including hospitals, nursing homes, emergency care facilities, and doctors offices, causing shut downs or restrictions upon health care services.  Water main breaks result in the shutdown of public and private facilities, including office buildings, government buildings, factories, and facilities requiring fire protection as a condition of occupation. Finally, water main breaks can have a huge impact upon the availability of water for fire departments to control or extinguish fires  in both urban and suburban areas. Thankfully, water main  breaks to date have not been accompanied by a major fire or other catastrophes in Atlanta.

Representatives of Atlanta currently predict that residents and businesses may be subject to as many as thirty (30) water main breaks each and every month. The “wait and see” attitude adopted by Atlanta and most other older cities, has a huge impact upon residents and cannot last forever.  At some point, every major city will need to “bite the bullet” and make major investments to replace or rehabilitate their aging water main infrastructure  While replacement and rehabilitation are both costly, with the latter being far less so, both require a financial commitment most cities are not prepared to make.