Air Quality

How To Drain Water from An Evaporative Cooler?

Drain Water from An Evaporative Cooler

Your evaporative cooler proved to be efficient this past summer, and you anticipate its longevity with proper care. When the swamp cooler is not in operation, it is crucial to drain water from an evaporative cooler to prevent potential damage caused by temperature fluctuations. Proper maintenance ensures that the evaporative cooler can operate seamlessly, even when not in use.

To assist you in this process, we have conducted thorough research, and the following are the recommended steps to drain the water from your sump/evaporative cooler:

Power and Water Supply Shutdown:

– Before opening the overflow/drain plug located at the bottom of the storage pan, turn off the power and water supply.
– Using pliers, grip the screw-nut from underneath and twist the screw in the opposite direction with your other hand.

Continue reading for detailed steps on how to effectively drain the water from your evaporative cooler.

Importance of Draining the Cooler:

Evaporative coolers, commonly known as swamp coolers, cool the air through a water cushion that facilitates evaporation. Failing to drain the collected water when the cooler is not in use can lead to stagnation and the formation of mold within the system. In colder climates, freezing temperatures can damage rotary components, with the circulation pump motor at risk of overheating and burning out due to frozen water, potentially causing motor winding melting.

Proper Water Draining Method:

To prevent these issues, follow these steps to empty the cooler water when it is not in use:

1. Turn off the Power:

– Switch off the device.
– In the electric breaker box, turn off the corresponding breaker.
– Cut off the water supply.

2. Empty the Reservoir Tank’s Water:

– Locate the reservoir plug/flood tube inside the reservoir pan.
– Secure the wrench to the screw-nut connected to that fitting beneath the pan.
– Wrap the reservoir plug around the screw nut at the top.
– Turn the screw-nut to the right and then to the left to loosen it.
– Once the plug is removed, the water should drain away.

3. Drain the Cooler Line:

– If your cooler has an outside hose, unscrew it at the spigot to allow the water reservoir to drain.
– If your cooler has a float valve, set it to the open position to enable water drainage.

Addressing Water Leaks:

If your cooler appears to leak water, consider the following possibilities:

1. Purge Pump in Your Water Cooler:

– Regularly change the water in the line using a flood/reservoir plug.

2. Float Valve Adjustment:

– If the float valve is too high, replace it to avoid excessive water entering the supply and cooler line.


By adhering to these maintenance practices, your swamp cooler should remain in optimal condition for an extended period. Whether it is window-mounted or on a rooftop, proper care is essential to avoid any damage during overwintering. Regularly check for leaks, ensure the tank and water line are reserved, and if needed, seek professional assistance for rooftop-mounted units.

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About the author


I am Ben , a seasoned HVAC specialist with over 6 of experience in the HVAC industry. I holds HVAC Certification and has a proven track record in providing expert advice on HVAC systems.

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