The Leaky Cast-Iron Pipe: A $420,000 Surprise You Can Avoid

A fellow investor recently bought an 84-unit garden apartment complex built in 1982 in suburban Dallas. The property was 96% occupied. Rents were below market. The deal looked like a home run.

Ninety days after closing, ground-floor tenants in Building 3 reported slow kitchen drains. Two weeks later, sewage backed up into four ground-floor bathtubs.

The investor called a master plumber. When they pushed a camera down the cleanout, they found old cast-iron sewer pipes rusted completely through beneath the concrete slab foundation. Dirt had collapsed into the line.

Trenching through concrete floors, replacing the lines, and putting tenants in hotels cost $5,000 per unit across the complex. That $420,000 unexpected repair erased two full years of projected cash flow.

The Due Diligence Rule We Never Break

On any building constructed before 1990, spend $1,500 to run camera scopes through main drain lines before removing inspection contingencies.

• Look for Pipe Belly and Cracks: Cast-iron typically rusts from the inside out after 40 years. PVC replacements last 100 years.
• Check Electrical Panels: While the plumber is scoping pipes, have your electrician verify there are no Federal Pacific or Zinsco breaker panels. Insurance carriers will cancel policies over them.
• Use Findings to Negotiate Credits: If lines are corroded, ask the seller for a $200,000 escrow credit at closing or walk away.

Real estate value isn't just about rent growth. It is about physical structures that stay dry, solid, and trouble-free.