An evaporative cooler pulls outside air through water-soaked pads. As the water evaporates it absorbs heat from the air, and the cooled, humidified air is blown into the space. The main components are the pads, a water reservoir, a pump, a distribution system, and a blower.

The Physics in One Paragraph

Evaporation requires energy, and that energy comes from the surrounding air as heat. Air passing across a wet surface gives up heat to evaporate the water, and comes out cooler and more humid than it went in.

How much cooling you get depends entirely on how much moisture the air can still absorb. Dry air absorbs a great deal and cools substantially. Humid air absorbs little and cools barely at all.

That single relationship explains everything about where this technology works and where it does not.

The Components

Cooler pads. The heart of the system — usually aspen fibre or rigid cellulose media. Air passes through them while water trickles down. Rigid media lasts longer and cools better; aspen is cheaper and needs replacing more often.

Water reservoir. The basin at the bottom holding the water supply, fed by a float valve that maintains level like a toilet tank.

Pump. A small submersible pump lifting water from the reservoir to the top of the pads.

Distribution system. Tubing and a spider or trough spreading water evenly across the top of each pad. Uneven distribution leaves dry sections that air passes through uncooled.

Blower. Moves air through the wet pads and into the space. Usually a squirrel-cage blower, belt-driven on larger units.

Bleed-off or purge line. Continuously discharges a small amount of water to keep dissolved minerals from concentrating. Easy to overlook and critical in hard water.

Why the Bleed-Off Matters Here

Evaporative cooling concentrates minerals by design — water evaporates and the dissolved solids stay behind.

Hill Country water is hard, so that concentration happens fast. Without adequate bleed-off, scale builds on the pads, in the distribution lines, and on the pump, reducing water flow and cooling while shortening the life of every wetted component.

Setting the bleed rate correctly for your water hardness is part of installing one properly.

The Exhaust Requirement

The component people forget is not on the unit at all.

An evaporative cooler pushes a continuous volume of air into a building, and that air has to leave. Without adequate relief — open windows, a dedicated exhaust, or a properly sized opening — the space pressurises, airflow collapses, and the cooler does nothing.

This is the most common reason a swamp cooler underperforms, and it is not a fault in the equipment.

Where It Works in the Hill Country

Central Texas is marginal for evaporative cooling. In late spring, before humidity climbs, it provides real relief. In July and August, when Gulf moisture arrives, performance drops off sharply — and the added moisture makes indoor air feel clammy at any temperature.

Good applications here are shops, barns, equipment bays, and covered outdoor areas — spaces with constant air exchange where humidity matters less.

For conditioned living space through a full summer, refrigerated air conditioning is the appropriate technology, because it removes humidity rather than adding it. For a shop or outbuilding, a ductless mini split usually beats evaporative cooling on both comfort and year-round usefulness.

Maintenance

Pads replaced on schedule, reservoir drained and cleaned, pump descaled, distribution lines cleared, and the system winterised before a freeze so nothing splits.

Neglected pads develop biological growth that gets blown straight into the building, which is an indoor air quality problem rather than only a performance one.

We service evaporative equipment. Contact 72 Degrees or call (830) 240-1835.