How to maintain an evaporative cooler

maintenance on evaporative cooler


You may be shopping for (or already have) an evaporative cooler to chill your place in hot weather. This is a very cool choice, indeed. An evaporative cooler is cheaper to use and operate than a traditional air conditioner (A/C) using refrigerant. They also use less electricity than an A/C.

As your house cools, you can feel proud knowing that you’re using a cost- and energy-efficient choice. To get the best performance from your unit, we’ll explain the evaporative cooler maintenance you’ll need to do periodically.


What is an evaporative cooler (swamp cooler)?

Evaporative coolers, also called “swamp coolers,” use fans to blow air through water-soaked pads, evaporating moisture into the air through a grill or ductwork. 

They may require a bit more maintenance than traditional air conditioning systems, but the savings in energy can help make up for this fact. As the name suggests, evaporative coolers work by evaporating water with water-soaked pads. They are best suited for hot, dry climates and are less effective in humid zones, which are already full of evaporated water.

Some benefits of evaporative coolers include:

  • They cool your house naturally and without the use of refrigerant chemicals, like those used with traditional A/Cs, which can hurt the ozone.
  • The filter pads used in swamp coolers can also act as air purifiers, removing airborne dust particles, debris and other pollutants.
  • They constantly bring a fresh air flow into a space and don’t just recirculate air like A/Cs.


How do evaporative coolers work?

Whether a rooftop unit, window unit or portable unit taken from room to room, an evaporative cooler draws in warm air and blows it out through water-soaked pads, cooling a hot, arid room or home by as much as 15 degrees. The highly absorbent pads are kept wet with a water pump drawing from a standing supply that needs to be replenished, or — in the case of rooftop evaporative coolers — they might be connected to the home’s water system for a constant supply of water.

The evaporative cooling works because the condensed water draws warmth from the surrounding area, leaving it cooler (or, technically, less warm). The unit’s blower sends the cold air through the standing unit’s grill or the duct system located throughout the house and connected to the rooftop unit.

Since the evaporative cooler uses a water pump to circulate the water to keep the pads wet — and not the refrigerant compressor used by air conditioning systems — it uses about a quarter of the energy A/Cs use to cool a room of the same size.

Without proper evaporative cooler maintenance, however, the cooling system can blow unhealthy bacteria (which can grow in wet and neglected absorption pads) into the air.


How to maintain your evaporative cooler

The evaporative cooler is not a closed system; its pads may have bacteria, mold and mildew growing in them, which can mix with the water passing through them and be blown into the house by the system. Regular evaporation cooler maintenance and cleaning are both a must. Here’s how you can maintain your evaporative cooler so that it works at its best. 

Clean the outside of your evaporative cooler

You should clean the unit’s exterior at the beginning of the hot season — before you start to use the evaporative cooler — and every few weeks thereafter until the end of the season. Just use warm water and a soft cloth — no surface cleaners or chemicals are necessary. 

Routinely clean and fill your evaporative cooler water tank

Change the water in the standalone and window units once a week using the drain plug in the bottom of the unit. You should take advantage of the change by cleaning the water tank as well using a cloth, warm water and soap. You can also use a 50-50 water-vinegar solution to get rid of any mineral deposits from hard water (even adding some baking soda if needed). If the evaporative cooling unit’s manufacturer allows it, you can add water treatment tablets to prevent the mineral buildup of hard water.

You should also ensure the tank water supply is full before each use (or check the water level and replenish it periodically during constant use). To keep rust and corrosion under control, you can treat the water tank with zinc anode tablets weekly or however often you need them.

Change the cooling pads in your evaporative cooler

You should change your evaporative cooler pads at least twice — at the beginning of the season and midway through. You may have to do it more often if you have hard water (full of minerals that leave deposits) or poor water quality. It’s probably time to change the fiber pads if the evaporative cooler smells murky or has a damp, stale odor. A fishy or swampy smell might be a warning that mold and mildew are growing — definitely time for a pad change and unit clean.

High-quality pads may not require frequent replacing; however, inspect the pads after frequent use and replace them if they are cracked or damaged in any way. You may opt to wash the pads and reuse them. You can do this by removing the filters, letting them dry out and then soaking them in a 50-50 water-vinegar solution (let them dry out again before reinstalling them). 

When the filter is removed for replacement or cleaning, take the opportunity to clean inside the filter compartment and on the exterior pad frame with soap and warm water.

Beginning-of-Spring evaporative cooler care

When setting up your evaporative cleaner in the spring as hot weather looms, you should tighten all connections with a screwdriver or wrench and lightly lubricate the cooler motor and blower bearings. 

You should also clean the filter, make sure the fan belt tension is right (not loose or sagging) and install new pads or use old ones if they are in good condition, with no damage or cracking. After filling the reservoir with fresh water, you can plug in the unit and enjoy the cool air.

Generally speaking, the evaporative cooler works best in hot, dry weather. If you can bear the heat, don’t turn it on until the thermometer inches above 85 degrees Fahrenheit.

End-of-season evaporative cooler care

When you finish using your evaporative cooler — usually sometime in the fall and just before the cooler weather — you should winterize the unit with a special routine. This includes turning off and unplugging the window or standalone unit, disconnecting the motor and pump and fully draining the water. Then, you should clean the filters, water reservoir and unit exterior, letting everything dry out before storage.

Wrap the cord up and store the evaporative cooler in a cool, dry place under a cover or in the product’s original box. 

Other swamp cooler maintenance and service tips

If you hear strange noises from the evaporative cooler or if the unit leaks water while running, it’s time to get professional service to ensure it operates safely and efficiently. 

As part of your spring maintenance schedule, you might want to show some TLC to the unit fan. Use a damp rag to clean the fan blades and the motor housing. The motor shaft should be sprayed with lubricant and the fan filter should be replaced.


Protect yourself from costly A/C repairs with Cinch

When you’re facing the summer heat, you want to make sure that your A/C is working well or can be repaired or replaced quickly if needed. That’s where Cinch Home Services can help. Our Home Protection Plans help cover the repair or replacement of a wide range of home appliances and built-in systems, including air conditioning systems.

Our plans also come with a 180-day workmanship guarantee and protection for unknown pre-existing conditions. Additional plan benefits even include a $25 credit to use toward filters for your A/C. In the middle of the hot season, you’ll be able to keep your cool with the peace of mind that a Cinch home warranty gives you. Get a free quote today.


An evaporative cooler provides an energy-efficient, eco-friendly way to cool you home. Here’s how to keep it in good working order.