How to Winterize a Swamp Cooler

Protecting an Evaporative Cooler From Freezing Temperatures

Swamp coolers

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In This Article
Project Overview
  • Total Time: 30 mins
  • Skill Level: Beginner
  • Estimated Cost: $40 to $60

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.

While this equipment has few maintenance needs, keeping it operating efficiently requires an annual winterizing process. When you winterize a swamp cooler, it helps prevent the water line from freezing and minimizes damage from condensation and rust. It also helps prevent heat loss through the cooler's vent. The following instructions show you how to winterize your own swamp cooler. You'll need to do some draining and cleaning, then you should cover the swamp cooler vents and insulate the cooler with a cover for the winter. The process should cost under $100 if you winterize it yourself and could cost in the general range of $150 if you call in a professional, depending on where you live.

What You'll Need

Equipment / Tools

  • Adjustable wrench or pliers
  • Bucket and sponges
  • Shop vacuum (optional)


  • Waterproof metal sealer (optional)
  • Replacement evaporative pads
  • Evaporative cooler cover (as needed)
  • Cardboard or insulation board


How to Winterize a Swamp Cooler

  1. Unplug the Unit From Its Power Source

    The appliance should be disconnected from its source of electricity before attempting the next steps.

  2. Disconnect the Water Line

    Turn off the water to your swamp cooler by locating the valve that controls the water supply to the cooler. Then 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 shutoff valve. 

    Next, disconnect the water line from the cooler, using an adjustable wrench or pliers. If possible, also disconnect the water line from the water supply valve and blow through it to remove any water in the line. A swamp cooler can freeze if there's standing water in the water line and that can also 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, drain it as best you can, then tuck it line into a storage place that is warm enough to avoid freezing.

  3. 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 cooler housing. Use a sponge and bucket to absorb as much water as possible from the pan.


    You may find a drain valve in the pan at the bottom of the 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. 

  4. Clean the Cooler

    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 buildup in the cooler pan, you can use a shop vac to clean it out before sponging it clean.

    As an optional step, 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.

  5. Change the Evaporative Pads

    The evaporative pads will need to be changed before the cooler is used again after the winter months; 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 differs depending on the design of the cooler, so consult the instruction manual for directions on how to do this. 

  6. 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. 


    To save money, you can use a tarp to cover your swamp cooler, tying it down with rope or bungee cords. Don't secure it so tightly that all airflow is eliminated, which will lead to rusted metal parts.

  7. Block the Vent

    The vent where the cooler blows air into the house 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-thick piece of cardboard or a piece of insulation board 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.

  • How long should swamp coolers last?

    Depending on the upkeep and quality of your swamp cooler, the appliance can last between five to 25 years.

  • At what temperature is a swamp cooler no longer effective?

    If it gets hotter than the mid to high 90s outside, the swamp cooler could have a tough time cooling your home.

  • Does mold grow in swamp coolers?

    Mold can grow in a swamp cooler. That's because pads stay wet and humid weather can cause mold and mildew to grow. Alleviate potential mold growth by checking humidity levels in your home and keeping the control moisture levels in the swamp cooler itself.