Desert garages are strange: bone dry most of the year, then monsoon humidity rolls in and your water heater starts sweating like a cold drink. That sweat looks alarming — water beading on the tank, dampness on the floor. Here is how to tell whether you are looking at physics or plumbing.
Why tanks sweat
Cold water enters the tank at ground temperature while humid air surrounds it. Moisture in the air condenses on the cold metal — same reason a glass sweats. It is most common on the cold inlet pipe and the lower tank shell, and it comes and goes with humidity, not with any plumbing failure.
The wipe test
Dry the entire tank and all visible pipes completely with towels. Check back in an hour or two. Condensation returns as a light, even film across broad surfaces. A leak returns as drips from a specific point — a fitting, a valve, a seam. One spot, persistent: that is a leak.
Where sweat shows up vs. where leaks show up
Sweat favors cold surfaces: the inlet pipe, the lower shell, sometimes the draft hood on gas units. Leaks favor joints: threaded fittings up top, the TPR valve, the drain valve, element gaskets. If the wettest point is a joint, suspect the joint.
The mineral tell
Condensation leaves no trace when it dries. A real leak leaves evidence: white mineral crust, green corrosion on copper, rust streaks. If you see crust or trails, water has been escaping from that spot for a while — that is not sweat, no matter how humid it has been.
When in doubt, watch it for a day
A single damp morning after a humid night is probably condensation. A drip that is still there tomorrow, in the same spot, after dry weather — call (833) 713-2101. We would rather confirm ‘just sweat’ than have you ignore a slow leak for a month.