How to Prevent Deposits in Evaporative Coolers


Evaporative coolers are usually used in warmer, dryer areas because they operate more efficiently in these climates. Water in these areas tends to be mineral rich and the evaporative process leaves behind deposits of calcium and alkaline on the cooler pads as well as on the interior of the cooler. The deposits also corrode and rust the metal housing and substantially reduce the operating life of the cooler. Preventing as much formation as possible of the mineral deposits improves cooling, air flow and the life of the cooler.

Things You'll Need

  • Stiff brush
  • Cleaning solution, one cup vinegar to one gallon water
  • Aspen cooler pads
  • Chemical scale removal treatment
  • Bleed-off valve
  • Plastic tubing
  • Remove the cooler panels from the cooler and scrub them thoroughly with a stiff brush and a solution of 1 cup white vinegar to 1 gallon of water. Take special care to clean the panel vanes of all build-up and debris.

  • Use Aspen cooler pads and change them as needed throughout the season. Aspen fibers soak up water, conduct it efficiently as a water curtain and improve the cooling effect. Filters should be changed as often as scale build-up occurs, usually two to three times per season.

  • Clean the water pan reservoir in the bottom of the cooler once a month during the season by turning off the cooler, draining the water reservoir pan completely, scrubbing it with a stiff brush and the solution of vinegar and water and rinsing thoroughly. Treat the water reservoir with a chemical scale remover, available from a home improvement store and according to package directions, to increase the solubility of minerals so they do not adhere as easily to the pads.

  • Do not use water for the evaporative cooler from a water softener because it is sodium rich from the softening process and will cause scale build-up.

  • Add a bleed-off valve to the water line that carries water from the reservoir back to the Aspen filters. This valve is available from home improvement stores and is installed on the water line, 6 inches up from the pump connection, and diverts a percentage of the recycled water through plastic tubing to an area of the lawn or garden that can accommodate the mineral rich water, such as Bermuda grass, salt grass or a water run-off.

Tips & Warnings

  • Begin each cooling season with a thorough cleaning of the evaporative cooler and paint the appropriate parts, according to label directions, with special paint from a home improvement store.
  • Use a canvas cover to shroud your evaporative cooler during the winter months and keep cold drafts from entering the house.
  • Always turn the cooler off at the switch inside the house as well as the switch located at the top if the unit, on the underside of the top cover.
  • Enlist someone to stay on the ground with a cellular phone to assist so it is not necessary to run up and down the ladder, increasing the risk of accidents.

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  • Photo Credit Brush image by Yuriy Rozanov from
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