Evaporative Cooler Leaks and the Water Damage They Cause

Why evaporative coolers leak in the first place

Evaporative coolers, often called swamp coolers, work by soaking pads with water and pulling air through them, so they run wet almost constantly during cooling season. That constant moisture is exactly why they're prone to leaks. Rooftop units sit on curbs or stands where the roof penetration, the water supply line, and the drain line all have to stay sealed against sun exposure, dust, and years of vibration from the fan motor. Any one of those seals failing sends water somewhere it shouldn't go. Common failure points include a cracked float valve that lets the water pan overfill, a clogged or misaligned drain line that backs water up instead of carrying it off the roof, mineral scale (common with Arizona's hard water) that cracks the pump housing or pads, and a bleed-off line that gets kinked or disconnected. Because the unit is usually out of sight on the roof, these problems tend to go unnoticed until water has already found its way inside.

Where the water actually goes once it's inside

A rooftop swamp cooler sits directly above living space, so a leak rarely stays contained. Water follows gravity and the path of least resistance, which is often not a straight line down. It can travel along roof decking, follow a duct chase, or run inside a wall cavity for several feet before it shows up as a stain on a ceiling or wall that's nowhere near the actual leak. That lag is what makes these leaks so deceiving: by the time you see a brown ring on the ceiling or paint starting to bubble, water may have been seeping in for weeks and already soaked insulation, drywall, or the top plates of framing. In homes with attic space between the roof and the ceiling, the attic insulation itself can absorb a surprising amount of water before any sign reaches the room below, which delays discovery even further.

Signs the leak has been going on longer than you think

A fresh leak usually looks different from one that's been active for a while. Watch for ceiling stains with a yellow or brown ring around the edge (a sign the water has dried and re-wet more than once), paint or texture that's bubbling or peeling rather than just discolored, a musty smell in the room the cooler serves, drywall that feels soft or spongy when pressed, and warped or darkened wood around window and door trim near the affected wall. Outside, check the roof jack and curb around the cooler for daylight gaps, rust streaks, or standing water after the unit has run. Inside the attic, if you can safely look, watch for dark or matted insulation directly beneath the cooler's footprint. None of these signs on their own prove serious damage, but together they usually mean the leak has been active long enough to matter.

What tends to happen if it's left alone

Standing or repeated moisture in framing and drywall creates conditions where mold can start to grow, typically within a couple of days of a material staying wet, and wood that stays damp over time loses structural strength as it swells, dries, and swells again. Ceiling drywall that has absorbed water enough times can sag or collapse under its own weight. None of this happens overnight, which is part of why these leaks are so easy to live with for a long time without realizing how much is happening behind the surface. If you're seeing any of the signs above, it's worth having the area opened up and checked rather than just patching the visible stain, since repainting over a stain doesn't address what's happening in the wall or attic behind it. You can read more about how water damage restoration works, or if a leak has already led to major water intrusion, see what reconstruction and rebuild involves for damaged framing or drywall.

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