Does a swamp cooler leak cause water damage?

How a swamp cooler leak causes water damage

An evaporative cooler, what most Las Vegas homeowners call a swamp cooler, works by pulling outside air through wet pads and blowing the cooled air into the house. To do that it needs a constant supply of water: a float valve keeps a reservoir pan filled, a small pump circulates that water up over the pads, and a supply line feeds the whole thing. Every one of those parts is a potential leak point, and they all sit on your roof in full desert sun.

The most common failures are a stuck or worn float valve that lets the pan overflow, a rusted or cracked pan that seeps from the bottom, a pump or distribution tube that sprays water past the pads, and a supply line fitting that drips. Because the unit runs for hours every day through the cooling season, even a minor drip adds up to gallons over a week. That water follows gravity into the ceiling and wall assemblies below, soaking paper-faced drywall, wood framing, and insulation. Those are all organic materials, which means they are food for mold once they stay wet.

Las Vegas adds its own twist. Our intense roof heat speeds up corrosion on metal pans and fittings, and the same dry desert air that makes evaporative cooling work also fools people into assuming a wet ceiling will simply air out on its own. It often does not. Water that wicks into a wall cavity or pools above a ceiling can stay trapped well after the surface looks dry, which is the same hidden-moisture trap that makes proper structural drying so important after any water event.

What to do next

If you find an active swamp cooler leak, the first move is to stop the water. Shut off the cooler and close its water supply valve so the pan stops filling. That alone halts the flow and buys you time to assess the damage instead of watching it grow.

Next, resist the urge to assume it will dry on its own. A wet ceiling that looks dry on the surface can stay saturated inside for weeks, and our dry desert air does not reach trapped moisture the way it reaches an open surface. The materials need a measured dry-out, not a hopeful wait. Within roughly 24–72 hours of getting wet, organic building materials can begin to grow mold, so the window to dry and save them is short. If water is actively spreading, that is an emergency, and the right move is to call us so we can stabilize the water first.

From there, the job is straightforward when handled correctly: map the moisture to find every wet area, dry the structure to a documented standard, and verify the result before repairs. When the leak has been steady and contaminated by a corroded pan or standing water, or when it overlaps with broader roof or plumbing intrusion, the work can extend into full flood restoration. Either way, the priority is the same: find the water you cannot see, remove it, and prove the structure is dry so the problem ends here instead of returning as mold.

One clarification worth making, since people often ask: the on-site inspection is the free part. If lab analysis is warranted, samples go to an independent third-party lab, billed at cost. We tell you plainly when testing is and is not needed, because guessing helps no one and we do not upsell work you do not require. Health and standards questions like this one are answered the same way our founder Craig Herrmann answers them, by the rulebook, since he co-authored the ANSI/IICRC S520 mold standard the industry follows.