Swamp Cooler Smells Bad? Musty, Fishy or New Pad Smell

Drain, flush and clean the water

Why. Phoenix’s and Portacool’s charts list stale or stagnant water as the first cause of a musty or unpleasant odor, and both say to drain, flush and clean the reservoir or tank. Hessaire says stagnant water can develop odors.

A portable cooler. Portacool says to shut the cooler down, disconnect the power and drain the tank once a week by removing the drain cap. With the tank drained and the power off, the media can come out so the tank can be cleaned, where dust may collect over time. Put the media back facing the way its label shows: Portacool says not to run the cooler unless all the media is securely in place. Hessaire says to unplug the unit first, drain and clean the tank at least weekly, and clean it with mild soap and water monthly.

Before it sits unused. Hessaire says to drain it completely and let it dry. Portacool says to store it with the tank wiped clean, the media and tank dry, and the cooler covered.

A roof or window cooler. DOE says to check the pads, filters, reservoir and pump at least once a month in hot climates where the cooler runs often, and its Building America guide says regular maintenance keeps the reservoir clean and odor-free. The guide also says to empty the pan whenever the cooler will sit idle for more than a few days, and in winter to shut off the water line, drain and clean the pan, and fit a cover.

How to drain it. Phoenix says to drain its coolers with the water supply and the power off, through a drain hose, and never onto a roof. Phoenix says never to wash the cooler cabinet with a garden hose, because water may harm the motor and pump or seep into the ductwork, and Portacool says to keep water out of the motor and electrical system when cleaning. Seeley’s Breezair TBQ and TBS coolers have Manual Drain, Drain and Dry and Autoclean settings on their MagIQtouch controller that drain the tank for you.

Clean or replace mildewed pads

Why. Phoenix’s and Portacool’s charts list pads that are clogged or mildewed as the second cause of an odor. Hessaire says a musty smell usually means mold or mildew on the cooling pads.

The fix. Portacool’s fix is to replace the media, and Phoenix’s is to check the bleed-off and clean or replace the pads. DOE says some paper and synthetic pads can be cleaned with soap and water or a weak acid, following the maker’s instructions. Hessaire says to replace pads that still smell after cleaning, and generally at least once a cooling season. DOE’s Building America guide says to replace torn, worn or mildewed pads.

Fitting new pads. On a downdraft metal cooler, Hessaire says new pads must sit at the very top of the panels, because pads fitted too low let water leak into the ductwork and the ceiling.

How often. DOE says to replace the pads at least twice a cooling season, or as often as once a month if the cooler runs all the time. Seeley says its honeycomb Chillcel pads last longer than other kinds, and to expect to change them every 7 or 8 years. Seeley warns that pads kept past their useful life can let water carry over into the ductwork and electrics.

Let the pads dry out every day

Pump off first. Portacool says to turn the pump off about 15 minutes before the fan at the end of the day, so the media dries. It says dry media at the end of the day lasts longer and helps control mildew, mold, bacteria and other odor-causing growth. Hessaire says to run the cooler in fan-only mode after use to dry out the pads. Seeley’s Drain and Dry setting on its TBQ and TBS coolers drains the tank and runs the fan for an hour at a time you choose each day.

Pads wet before the fan. Phoenix’s chart lists pads that are not completely wet before the cooler starts as a cause of odor, and its fix is to turn the pump on for several minutes before starting the cooler.

What stops algae. Munters, writing about large commercial pad walls, says algae needs light, moisture and nutrients, and cannot live when the pad is bone dry. It says to let the pads dry completely once every 24 hours, to turn the pumps on last and off first, and to cover the sump to keep out dirt and light. It also says not to use phosphate scale control agents or detergents in the pads, because they break down into food for algae, and to clean old algae and rotted pads out of the system.

New pads: give them time

A new cooler or new pads. Seeley says its Chillcel pads are a bit smelly when a new cooler is first turned on, and the smell does not last long. Portacool says new media may give off a slight smell that lessens in time, and that it does not let harmful chemicals into the air.

Speeding it up. Seeley’s fix for odor from new pads is the Pad Flush setting on its MagIQtouch controller, or draining the tank now and then during the running-in period so fresh water flushes the pads.

Look for smells pulled in from outside

Why. A swamp cooler blows outdoor air into the house, so it brings in whatever is near it. Phoenix says not to place its industrial and commercial coolers near vent pipes or kitchen exhaust, because odors or fumes may be drawn into them, and to install them where only fresh outside air can enter.

Let the air out. Seeley says the air a cooler blows in collects moisture and impurities and must leave the building, so keep doors or windows open. More on that in a swamp cooler not cooling.