Leaks & Building

BuildingWrench repair guide

Leaks & Building

Water Stain Under an HVAC Unit: Roof Leak or Condensate?

A ceiling stain near HVAC equipment can come from condensate, chilled-water piping, roof leaks, sweating ductwork, or plumbing. The timing of the leak—rainy weather versus cooling operation—is one of the fastest ways to narrow it down.

Last reviewed 2026-09-12 · General facility-maintenance information, not a substitute for site procedures, manufacturer instructions, codes, or qualified professional judgment.

Routine investigationSkill: BeginnerTypical time: 15–40 min
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Safety boundary

Protect occupants first. Avoid unsafe roof, ladder, ceiling, electrical, or structural access while tracing water.

Full troubleshooting steps are in Pro

The safety boundary, quick answer and stop-work conditions above stay free. Pro opens the likely causes, symptom table, step-by-step procedure and preventive maintenance for this guide.

Stop and call a licensed professional when

  • Water near electrical equipment
  • Insulation extensively saturated
  • Active chilled-water leak suspected
  • Roof access unsafe
  • Concealed drain repair needed

Mistakes, FAQ, parts and tools

Pro opens the rest of this guide: common mistakes, field FAQ, the parts list, and the tools for the job.

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Leaks & Building

Water Coming Under an Exterior Door: How to Find the Entry Path

Water at an exterior door can come through the threshold, failed sealant, door sweep, jambs, masonry joints, or exterior drainage that sends water toward the opening. Start outside and follow the path instead of immediately replacing weatherstripping.

Leaks & Building

Commercial Roof Leak: First Response Checklist for Maintenance Staff

The first job during a roof leak is not permanent repair—it is protecting people and property, controlling interior water, documenting the leak, and giving the roofer enough information to find the source. Safe documentation during the event often saves hours later.

Leaks & Building

Water Leak: Find the Source and Control the Damage

Stop the water if there is an accessible isolation valve, keep people and electricity away from it, then trace the path from the lowest wet point up to the highest. Condensate, roof, supply piping, and drain leaks all look the same on a ceiling tile.

Leaks & Building

Ceiling Leak After Rain? How to Trace Where the Water Is Coming From

A wet ceiling tile often is not directly below the exterior leak. Rainwater can travel along roof decking, framing, conduit, piping, insulation, or wall cavities, so document the wettest point and trace the path upward and outward.