How to Winterize an Evaporative Cooler

Metal grate swamp cooler
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Winterizing Protects Your Evaporative Cooler

In many parts of the country, home cooling is provided by an evaporative cooler rather than standard air conditioning. Also known as a swamp cooler, an evaporative cooler is a fairly simple device that cools air through the physics that causes water to absorb heat from the surrounding air as it transitions from liquid to gaseous form. Evaporative coolers are especially efficient in dry climates, and they are remarkably simple and energy-efficient devices. But although it has few maintenance needs, keeping a swamp cooler operating efficiently requires an annual winterizing process.

Why You Should Winterize Your Evaporative Cooler

Winterizing an evaporative cooler offers several benefits:

  • Prevents the water line from freezing and requiring replacement the following spring
  • Prevents damage due to condensation and rust
  • Prevents heat loss from the cooler vent

Tools and Supplies You Will Need

  • Adjustable wrench
  • Channel-lock pliers
  • Bucket and sponges
  • Shop vacuum (optional)
  • Watertight metal sealer (optional)
  • Replacement evaporative pads
  • Cover for evaporative cooler

Disconnect the Water Line

The first step to winterizing an evaporative cooler is to shut off the water and disconnect the water supply line. 

Locate the valve that controls the water supply to the evaporative cooler and turn it off by turning the handle clockwise. The valve and water line are often located somewhere where they are protected from the cold, such as in a crawl space under the house. Tracing the water line back from where it connects to the cooler will lead you to the control valve. 

Then, disconnect the water line from the cooler. If possible, also disconnect the water line from the water supply valve and blow through it to remove any water in the line. Standing water in the water line can potentially freeze and cause the line to rupture.

If feasible, remove the water line entirely where it is secured to the house or to framing members and coil it up for storage. If you can’t easily disconnect the waterline, be sure to drain it as best you can before storing it.

Tuck the water line into a storage place that is warm enough to avoid freezing.

Drain the Water

It is important to drain all of the standing water at the base of the cooler to prevent corrosion and possible damage over the winter months. To do this, first, remove one or two of the cabinet sides on the evaporative cooler. Use a sponge and bucket to absorb as much water as possible from the pan.

  • Tip: You may find a drain valve in the pan of the evaporative cooler, but removing the plug and trying to reseal it can sometimes lead to leaks. Sponging out the pan gets more water out and eliminates the likelihood of leaks in the drain valve seal. 

Clean the Cooler

You can also use the sponge to clean away any dirt and grime along the inside walls of the evaporative cooler. Cleaning it now will simplify the work of starting up the cooler next spring. 

If there is a lot of mineral and dirt build-up in the cooler pan, you can use a shop vac to clean it out before sponging it clean.

  • Optional: When the pan is dry, coat the bottom of the pan with a waterproof metal sealer to prevent rusting. Or, you can wait until spring to check for leaks and seal them.

Change the Evaporative Pads

The evaporative pads will need to be changed before the cooler is used again after the winter months, and you can do it now or when you de-winterize the appliance in the spring. Some people like to change the pads as part of the winterizing process so that when spring comes they can just hook up the water supply and be ready to go. 

The precise method for replacing the pads will differ depending on the design of your evaporative cooler, so consult the instruction manual for directions on how to do this. 

Install a Winter Cover

Protecting your evaporative cooler with a cover will protect the unit from the elements during the winter months. Measure your cooler, then buy a cover that fits snugly over your model without being fully airtight.

A cooler cover is easy to install by simply slipping it over the cooler and tying it down along the bottom and sides of the unit. Many covers protect against rain, snow, sun, and dirt and can be reused year after year.  The vent panels on the side of the swamp cooler will provide enough airflow to reduce condensation that can damage the metal, and also prevent wind lofting that might cause the cover to fly away. 

  • Note: To save money, you can use a tarp to cover your swamp cooler. A tarp can be tied down with rope or duct tape. But don't tie down the tarp so tightly that all airflow is eliminated. Some air movement is necessary to prevent condensation that can rust the metal parts.

Block the Vent

The final step to winterizing your swamp cooler is to cover the vent where the cooler blows air into the house. This vent is a possible source of heat loss in the winter, so it is a good idea to close and seal it during the winter months.  

An easy way to do this is by cutting a double piece of cardboard or a piece of insulation to the size of the opening. From inside the house, remove the vent cover and install the cardboard or insulation into the opening and then put the cover back on.

Your evaporative cooler is now ready for winter. Remember, though, to reverse the process the following spring to prepare your cooler for the summer months.