How-to
Evaporative coolers at spring startup and winter shutdown
Clean or replace the pads, check the belt, nozzles, tray and float in spring, drain the pan whenever the cooler sits idle, and drain, dry and cover it for winter.
Satisfy+ Editorial · Published September 21, 2026 · 3 min read · 1.5 hr to do · Under $100
At a glance
- Twice a year
- Spring startup and winter shutdown
- Spring
- Pads, belt, nozzles, tray and float
- Idle for a few days
- Drain the pan
- Winter
- Water off, pan drained and dried, unit covered
An evaporative cooler, or swamp cooler, pulls outside air through thick pads soaked with water. As the water evaporates, the air cools before a blower sends it into the house. It works best where the air is hot and dry, and it uses about a quarter of the energy of central air conditioning.
The water needs care too. Debris, rust and mineral scale cut how well it works, and a dirty reservoir smells. Do the upkeep at least twice a year: when you start the cooler in spring, and when you shut it down for winter.
What you need
- New cooler pads, if the old ones are torn, worn or mildewed
- White vinegar and a small brush, for the nozzles
- A bucket and rags, for the pan
- A plastic or canvas cover, for winter
- The cooler's manual, for its belt and lubrication instructions
Steps
- 1
Decide who does it
Ground- and wall-mounted coolers are within reach for you. A cooler on the roof is hard to get to, so have a cooler service do the spring and winter work on it.
5 min
- 2
Turn it off
Switch the cooler off and turn off its power before you open the cabinet.
2 min
- 3
Clean the cabinet and replace worn pads
Clean out the cabinet and look it over for damage. Clean the pads, or put in new ones if they're torn, worn or mildewed.
30 min
- 4
Check the belt and the blower
Check the fan belt's tension, and lubricate the blower motor's bearings as the manual says.
10 min
- 5
Clean the nozzles
Check that the water nozzles are aimed to soak the pads, and clean off mineral scale with vinegar.
15 min
- 6
Check the tray and the float
Make sure the tray holds water without leaking, and repair any holes or cracks. Check that the float works, so the water stops at the right level.
10 min
- 7
Open a way out for the air
When the cooler runs, open windows or doors so the air has somewhere to go. It replaces all the air in the house every 2 to 3 minutes. Air flows toward the open windows, so open them in the rooms you want cooled.
1 min
- 8
Drain it when it sits idle
During the summer, empty the pan whenever the cooler will sit unused for more than a few days. Standing water breeds mosquitoes and bacteria, including Legionella, which causes Legionnaires' disease.
10 min
- 9
Shut it down for winter
Turn off the water line to the cooler. Drain the pan, clean it, and let the whole unit dry completely. Clean off mineral deposits, especially around the fan, the nozzles and the tray. Put a plastic or canvas cover over the entire unit, and close the dampers if it's connected to ducts. Take a window cooler out of the window and store it, so the window can be shut.
30 min
Look after the evaporative cooler through the year
- Clean or replace the cooler pads and check the belt
- Drain the cooler pan before it sits idle for a few days
- Winterize the evaporative cooler and cover it
Hard water
If your water has a lot of minerals, scale builds up faster. A bleed-off valve drains some water to keep minerals down, but it can raise the cooler's water use by 10 to 50 percent. An auto-flush system, or dump pump, empties the pan and refills it with fresh water every 8 to 12 hours of running, and uses less water. Hard water and the scale it leaves covers water hardness.
FAQ
How often should I service an evaporative cooler?
At least twice a year, at spring startup and winter shutdown.
How do I winterize a swamp cooler?
Turn off its water line, drain and clean the pan, let the unit dry, clean off mineral deposits, then cover it. Close the dampers if it's ducted, and take a window unit out of the window.
Why does my swamp cooler smell?
A dirty reservoir and standing water. Drain the pan when the cooler will sit idle for more than a few days, and clean it at startup and shutdown.
Sources
Checked October 20, 2026
- U.S. Department of Energy, Building America Solution Center. Evaporative cooling systems (2026)
- HVAC
- Owner
- Southwest
- Either
- Hot dry
