Every monsoon season we get the same call: "My water heater is sweating — is it leaking?" Sometimes it is just condensation. Sometimes it's a leak wearing a condensation costume. Here's how to tell.
Why heaters sweat in Arizona
When humid monsoon air hits a cold tank — especially a tank full of cold water after heavy use — moisture condenses on the steel exactly like a cold glass on a summer day. Garages with poor ventilation make it worse. This kind of sweating is light, widespread, and temporary.
The paper-towel test
Dry the tank completely with towels, then wrap suspect areas with dry paper towels secured by tape. Check in 2–4 hours: uniform dampness across the tank suggests condensation; a wet spot growing from one point — a valve, fitting, or seam — means a leak.
Five clues it's a real leak
- Water returns to the same spot after drying, even in dry weather
- Rust stains or mineral crust mark the spot
- Dripping is localized to a valve, joint, or the tank base
- The puddle grows rather than evaporating
- You hear hissing or see a steady drip stream
Five clues it's condensation
- Light, even moisture over large tank areas
- Appears during humid weather and vanishes when it's dry
- Cold supply pipes are sweating too
- No staining, no crust, no localized drip
- The floor dries on its own within hours
When in doubt, get certainty
A $89–$149 diagnostic with moisture-meter verification beats guessing wrong in either direction. Call (833) 713-2101 and we'll prove it one way or the other.
Related Questions
Can condensation damage my garage?
Light sweating evaporates harmlessly. But persistent dampness — even from condensation — can feed mold in drywall and rust the tank jacket, so improve ventilation regardless.
Why does my heater only sweat in summer?
Monsoon humidity plus cold incoming water is the recipe. It's the most common in July through September in the East Valley.
My T&P discharge pipe is dripping — is that condensation?
No — discharge-pipe dripping is never condensation. That's the valve weeping and it needs professional attention.