Why seventy year old copper starts to go
Houses of this era were generally plumbed in copper, which replaced galvanized steel as the standard supply material through the 1950s. Copper is a good pipe and it lasts a long time, which is why it is still in service in these houses at all. But it does not last forever, and the way it fails is specific.
Pinhole leaks. Over decades, water chemistry and flow velocity gradually erode the inside wall of the pipe, usually worst at bends and at points where the flow is turbulent. The result is a small hole rather than a dramatic split, and a small hole under constant pressure does a surprising amount of damage before anybody notices. One pinhole in a seventy year old copper system is often the first of several, because the whole run has had the same seventy years.
Freeze splits. Copper has no give. Where a run passes through an exterior wall, an unheated garage or an attic, a hard freeze splits it cleanly. These are usually a single section replacement rather than a system problem, provided the cause gets dealt with at the same time.
Failures at later transitions. Seventy years means renovations, and renovations mean CPVC or PEX joined to the original copper. Every junction between two materials is a candidate for failure.
The practical question on a Fernwood call is usually whether you are looking at one failure or the first of many. That depends on the condition of the whole run rather than the state of the one spot that leaked, and it gets assessed rather than assumed. See burst pipe replacement for how that decision is made.
