Cambridge water main floods from cast iron pipe failure

Cast iron pipe graphitizes (decarbonizes) over ~100 years, losing strength. Five percent of Boston's water lost through leaks; periodic main breaks cause ten-million-dollar downtown damage events.

We switched to PEX-A and B. We use cast iron, but cast iron pipe that we put in the old days for water has been switched to concrete-lined, because the concrete has a better lifetime than the cast iron. After about a hundred years, cast iron will start to decarbonize — they call it graphitize — and lose its strength. It turns out about five percent of all the water going through the streets of Boston is lost through leaks. There are leaks all over, and they've got old concrete pipe, and every now and then a concrete water main will burst and do ten million dollars worth of damage downtown and tie up traffic. We've got aging infrastructure.

Tom describes water main repair crews shattering 100-year-old cast iron mains with a sledgehammer — illustrating both cast iron brittleness and the longevity of legacy infrastructure. Connects to recurring corpus theme of aging Boston/Cambridge buried infrastructure.

Have you ever seen the water main guys repairing a leak? They get down in the hole, uncover this big cast iron water main, and when they need to cut it out, they don't have to saw it — they just take a sledgehammer and hit it. It just shatters. That's what carries our water, and that's why you have big floods in Cambridge. Some of those cast iron pipes are 100 years old. So they've gotten a fair amount of service.