Repairing a commercial leak is a choice, not a single procedure. A failed section of copper in an accessible ceiling gets cut out and replaced in an hour. The same failure under a slab in an occupied ground-floor unit means either breaking concrete in someone’s space or rerouting the line overhead and abandoning the old run. Both are legitimate, and they cost very different things.

What tips the decision is history. If this is the first failure on an otherwise healthy line, spot repair is almost always right. If the same run has leaked before, or the material is at the end of its life, repairing one spot means coming back for the next one, plus another round of damage to whatever sits below. That’s when rerouting stops being the expensive option.

The other half of the job is containment. In a commercial building, the leak damages the space around it while we work, so drying, protecting finishes, and keeping the affected area sealed off from tenants and customers is part of doing this properly rather than something somebody else handles later.

Most commercial leaks start at a specific weakness rather than randomly. Joints and fittings take stress from thermal movement every time hot water runs. Sections where a line rubs against a strap, a stud or a slab penetration wear a thin spot over years. Undersized lines carrying high velocity water erode from the inside at every elbow, which is why copper failures cluster at direction changes.

Under slab, the mechanism is different. Copper in direct contact with concrete or damp soil corrodes from the outside, and any small manufacturing flaw becomes a pinhole under decades of pressure. There’s no warning because there’s nothing to see, which is why an under-slab failure usually announces itself as a water bill or a warm floor rather than a drip.

In stacked coastal buildings, one more factor matters: what’s below. A riser leak in a condo, hotel or apartment building doesn’t stay in the unit where it started. Water finds the floor penetration, follows it, and shows up two or three levels down. That’s why a small leak in one unit turns into a claim involving several, and why speed on repair matters more in these buildings than the size of the failure suggests.