How to Soften Hard Water in Evaporative Coolers

Hunker may earn compensation through affiliate links in this story.

You may know your evaporative cooler as a swamp cooler, but the words refer to the same type of machine, one that reduces air temperature via water evaporation. These machines work by drawing hot, dry air through cool pads. The key to an efficient cooler is keeping those pads free of swamp cooler calcium buildup that happens if your water is hard. Softening the water used in your cooler means less mineral buildup and less swamp cooler maintenance. You can use a commercial water softener product or attach a water softening machine to the cooler.

How to Soften Hard Water in Evaporative Coolers
Image Credit: Witthaya Prasongsin/Moment/GettyImages

Swamp Cooler Maintenance

When hot, dry air is directed through something wet, the water in the wet thing evaporates, causing the air to cool. The evaporative cooler improves this basic process with mechanical parts. Swamp coolers use water pumps to keep the wet pads wet and fans to distribute the cool air around the home. This turns evaporation into a very efficient air cooling device. These are extremely popular in dry desert areas.

Although water is critical to the swamp cooler evaporation process, it can also damage the efficiency of the machine. Hard water in the cooler is the most important example of this.

Swamp Cooler Calcium Buildup

Hard water refers to water that contains a high concentration of calcium deposits and minerals. Swamp cooler calcium buildup can damage the mechanical parts of an evaporative cooler, dramatically reducing the efficiency of the cooler. You will see tell-tale spots, such as mold on the filters and marks on the pads. Regular swamp cooler maintenance, if you have hard water, includes checking and changing pads and filters.

To avoid the problems of hard water, you can use filtered water, which is water that has been cleaned of excess calcium and mineral deposits. Or you can use distilled water – water that has been turned into steam and then cooled again to remove salt, calcium and other minerals. This is even better than filtered water for use in an evaporative cooler because of its total lack of hard-water deposits. A third option is to use a water softener for the evaporative cooler.

Water Softener for Evaporative Cooler

If you are not able to get reasonably priced filtered or distilled water for your swamp cooler, your only choice may be to soften the hard water you have. Adding water softener to hard water dissolves some of the unwanted minerals.

You can purchase products that will reduce the hardness of your water. This type of evaporative cooler water treatment is added to the water reservoir in the cooler. It will reduce the hard-water deposits left behind on pads and filters. Use the product according to package directions. Alternatively, you can buy and install a unit to soften the water in the recirculating water line of your air conditioner.


From Alaska to California, from France's Basque Country to Mexico's Pacific Coast, Teo Spengler has dug the soil, planted seeds and helped trees, flowers and veggies thrive. A professional writer and consummate gardener, Spengler has written about home and garden for Gardening Know How, San Francisco Chronicle, Gardening Guide and Go Banking Rates. She earned a BA from U.C. Santa Cruz, a law degree from U.C. Berkeley's Boalt Hall, and an MA and MFA from San Francisco State. She currently divides her life between San Francisco and southwestern France.

View Work