Beginning in the 19th and into the 20th centuries, cities utilized cast iron plumbing for their water and sewage systems. While it proved to be a durable choice, and a significant improvement over the previous system, over time the pipes became susceptible to corrosion, forming a condition known as tuberculation in pipes.
What Causes Tuberculation?
Tuberculation in pipes forms from iron-oxidizing bacteria that congregate in water lines. As the bacteria metabolize, a brown slime builds up, coating the interior of the pipe. This sludge left behind by the bacteria is known as tubercles. Aside from the build-up, the primary indicator of tuberculation in a pipeline is the pitting found along the interior.
Customers may notice tuberculation before the corrosion is severe enough to break the line entirely. Plumbing fixtures with a red or reddish-brown stain is an indicator that bacterial elements are at works tearing down the iron. Some may see staining in their laundry or what appears to be dirty water coming from the tap.
How to Fix Tuberculation
There are ways to clear the area and keep the existing pipes in service for a time. The first step is the use of low-pressure cleaning using abrasive jetting machinery (AJM) to remove the slime from the interior walls. Pigging the pipe with high-powered cleaners also eliminates the build-up.
Corrosion weakens the pipe wall, making it less structurally sound than before. Cleaning with high-powered washers softens the surface further, which is why AJM is the first choice for clearing corrosion build-up.
While cleaning the line is necessary, other efforts must be put forth to prevent the reappearance of tuberculation in pipes. If workers do not take preventative measures, they have to replace the line sooner than expected.
How to Prevent Tuberculation
According to the Ductile Iron Pipe Research Association’s (DIRPA) May 2014 article, “tuberculation is a thing of the past.” The group reasons that cement-mortar lining prevents tuberculation from being problematic. In fact, it is recommended that once a line is pigged or mechanically cleaned, it should, in fact, be lined by AWWA C602 cement mortar.
Lining existing cast iron pipes is the best preventative method available with the current technology. It is more cost effective than replacing the cast iron pipes with new lines.
Unlined pipelines should be monitored and cleaned regularly. Many cities use pigs to help to collect data on wall thickness and tubercle build-up. Once the pipe walls become too thin, however, replacement is the only viable option. When replacement occurs, cities typically use pipe bursting techniques to remove the old line while running new.
Tuberculation in pipes occurs over time in cast iron pipes. While many of these water and sewer lines are over 100-years-old, they are still in working condition if worker accurately maintains them. Periodic cleaning helps prevent the build-up of the brown sludge associated with tubercles. However, the best preventative method available it to line the pipelines with cement-mortar lining. The new coating helps to provide a barrier between the bacteria in the water and the cast iron pipe wall.