Sheldon Thomas is proprietor of Clear Water Legacy. Clear Water Legacy Inc. is a water distribution operator training service, created by Sheldon, retired Manager of Water Distribution for the City of Hamilton, Ontario, Canada. Mr. Thomas devoted more than a quarter century to operating and then managing Hamilton’s aged, unique, and complex water infrastructure.

Sheldon spoke on: “Trouble Underground: the Pipes are Calling” a story of the decaying water main infrastructure in Hamilton. To set the tone for his talk, Sheldon’s first slide showed a fire hydrant with dirty, rusty water gushing out of it. Most of the water pipes in Hamilton are made from cast iron. Although they are initially pristine, after about 15 years or so they begin to corrode.
After about 100 years, the cast iron pipes are almost totally occluded.
The rust contains evidence of iron bacteria, sulfur reducing bacteria, sediment (solids) and a biofilm (a gelatinous layer).
Sheldon described the process of tuberculation. Tuberculation is a form of internal corrosion and bio-film contamination which develops in iron pipes and restricts water flow. It can be a breeding ground for bacteria. The town of Walkerton, Ontario provides a case in point. In 2000, E-coli had infiltrated the municipality’s iron-pipe water network, and purging it from the system was extremely difficult. The final Walkerton report ordered the town to take measures to reduce biofilms.

As bad as they look though, the water is safe to drink because chlorine is added to disinfect the water. And, of course, it is routinely tested.
The cast iron pipes are the main ones that freeze and break. They get weakened by the rusting and then the water freezing causes it to expand and burst the pipes. The process is called graphitization (the iron in the pipe forms rust leaving behind the weaker carbon (graphite) that was used in the iron making process). 
In summary, Sheldon reported that the city needs to invest millions of dollars to either re-line or replace the ageing cast iron pipe network.