How often should I maintain my evaporative swamp cooler?

Question

Accepted Answer

Twice a year: a full service before cooling season starts and a winterisation after it ends. Evaporative equipment needs more hands-on attention than refrigerated air conditioning, and skipping either visit causes predictable problems.

The Spring Startup

Before the season, the system gets opened up and gone through.

Pads are inspected and replaced. Aspen pads generally need replacing every season; rigid media pads last longer but eventually clog with mineral deposits and lose their ability to hold water evenly.

The reservoir is drained, scrubbed, and refilled. Over a winter of sitting, sediment settles and biological growth develops in any water left behind.

The pump is checked and descaled, the water distribution lines are cleared, and the float valve is adjusted to hold the correct level. Uneven water distribution leaves dry sections of pad that air passes through completely uncooled — a common cause of poor performance that looks like a sizing problem.

Belts and the blower motor are inspected on belt-driven units, and the bleed-off rate is verified.

The Fall Winterisation

This visit matters more in the Hill Country than owners expect.

The system is drained completely, the water supply line is shut off and drained, and the unit is covered. A water-filled evaporative cooler left charged through a hard freeze will crack, and the supply line feeding it is typically exposed.

Roof-mounted units also get their covers checked, because an uncovered cooler is an open hole in your roof collecting rain all winter.

February 2021 demonstrated what happens to unwinterised water-bearing equipment in this region.

Why Hard Water Drives the Schedule

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

Hill Country water is hard, so that concentration happens fast. Scale builds on pads, in distribution lines, and on the pump, reducing water flow and cooling capacity while shortening the life of every wetted component.

A correctly set bleed-off continuously discharges a small amount of water to keep concentration in check. Set too low and the unit scales rapidly; too high and you waste water. That setting depends on your actual water hardness, which is why we test rather than guess.

Homes with a water softener feeding the cooler see dramatically less scale.

What You Can Do Between Visits

Check the water level periodically and confirm the float valve is holding.

Look at the pads mid-season. If they are crusted white or have dry channels where water is not reaching, that needs attention before performance collapses.

Listen for the pump. A pump that has scaled or seized leaves the pads dry, and the unit becomes an expensive fan blowing hot air.

Why Neglect Is an Air Quality Problem

This is the part worth taking seriously.

Pads that stay damp and are never replaced develop biological growth, and that air is blown directly into your building. Standing water in an uncleaned reservoir is also a mosquito breeding site through a Hill Country summer.

A neglected evaporative cooler is not merely underperforming — it is actively degrading indoor air quality.

An Honest Note on the Technology

We service this equipment and we will also tell you where it belongs. Evaporative cooling works well in dry conditions and poorly in humid ones, and Central Texas humidity in July and August limits it substantially.

It suits shops, barns, equipment bays, and covered outdoor areas. For conditioned living space through a full summer, refrigerated air conditioning removes humidity rather than adding it, and for a shop a ductless mini split is usually the better long-term answer.