Pipe sweating or condensation

Symptoms

• Pipe feels wet or drips even though there's no visible leak source
• Problem worsens in summer or humid weather
• Puddle forms below a cold water pipe over time
• Pipe surface feels noticeably cold to the touch

Likely causes

• CommonWarm, humid air contacting a cold water pipe surfaceThis is basic condensation, the same effect as a cold drink glass sweating on a humid day.
• CommonPoor ventilation in the space around the pipe (basement, crawlspace)Enclosed damp spaces trap humidity against pipe surfaces more than open, ventilated areas.
• PossibleUninsulated cold water line in a humid areaInsulation acts as a barrier preventing warm air from directly touching the cold pipe surface.
• Less commonActual leak mistaken for condensationIt's worth confirming the water isn't coming from a fitting rather than the pipe surface generally.

What to do

1. Dry the pipe completely and watch it over the next hour to see if moisture reappears evenly along the pipe (condensation) or specifically at a joint (a leak).
2. If it's condensation, wrap the affected pipe sections with foam pipe insulation sleeves, sized to fit snugly.
3. Seal the seams of the insulation with the adhesive strip or tape included with the product.
4. Improve ventilation in the space if possible, such as running a dehumidifier in a damp basement or crawlspace.
5. Check for and fix any other sources of excess humidity nearby, like a leaking foundation or poor drainage.
6. Monitor over the following weeks, especially during humid weather, to confirm the insulation resolves the sweating.
7. If moisture appears specifically at a fitting rather than along the pipe body, treat that separately as a leak.

Tools and parts

• Utility knife (to cut insulation)
• Towel

When to call a pro

Not usually needed; a plumber is only necessary if you find the moisture is actually coming from a leaking joint rather than condensation.

Safety