`Boston and New York cast-iron water main failures`

A lot of the cast iron we put in a hundred years ago — and there's a lot of that pipe out there — has been doing pretty well for a hundred years. The reason is, if it had been steel it would corrode within thirty or forty years. Remember, that's the Achilles heel of steel. Cast iron has got three percent silicon and it forms this glassy silicon dioxide layer — it is glass basically on the surface — and that protects it from corrosion for a while. But after about a hundred years, depending on the quality of the water, that starts to break down too. Boston is an old city that started putting water pipes in a hundred years ago, and they have hundreds of miles of cast iron pipe water mains all through the city of Boston and towns hereabout.