Leaks & Building

BuildingWrench repair guide

Leaks & Building

Cold Pipe Sweating: Condensation or a Plumbing Leak?

Water on a cold pipe is often condensation, especially on chilled-water and cold-water lines in humid spaces. Dry the pipe and watch where moisture reforms before calling it a leak.

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

Routine facility fixSkill: Beginner-friendlyFormat: Diagnose → Fix → Test
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Safety boundary

Protect occupants first and 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

  • Active pressurized leak is suspected
  • Insulation is extensively saturated
  • Mold or ceiling damage is developing

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 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.

Leaks & Building

Supply Diffuser Sweating: Why It Happens and What Maintenance Can Check

A sweating supply diffuser usually means the diffuser or nearby duct surface is below the room's dew point. High indoor humidity, missing duct insulation, air leakage around the boot, low supply temperature, or poor airflow can all contribute.

Leaks & Building

Basement or Lower-Level Water After Heavy Rain: First Checks

Lower-level water after storms often comes from exterior drainage, foundation joints, floor drains, sump failure, window wells, or sewer backup. First separate clean rainwater from sewage and electrical hazards.

Leaks & Building

Cracked Exterior Sealant: When to Recaulk and When Not To

Failed exterior sealant can admit water and air, but smearing new caulk over old material rarely lasts. Proper repair means removing failed sealant, preparing the joint, and preserving designed drainage paths.