Swamp cooler start-up: an 8-step spring checklist

PNNL says evaporative coolers need maintenance at least twice a year, and spring start-up is one of those times. Work through these eight steps in order. Use your cooler's manual for model-specific details.

1 Power off and uncover the unit

Switch off or unplug the cooler before you open it. MasterCool's manual includes unplugging the unit among its seasonal steps. Then remove the winter cover.

Next step: Keep the cover for fall; the winterizing checklist in the Albuquerque guide uses it again.

2 Clean the pan and cabinet

UA Extension and PNNL both start spring with cleaning the pan and cabinet and checking them for damage. PNNL adds: make sure the tray is water-tight and repair any holes or cracks.

Next step: If the pan is rusted through, ask about repair or replacement when you request a free quote.

3 Replace or clean the pads

Install new aspen pads (UA Extension), or rinse rigid media with a garden hose (MasterCool). MasterCool says to install rigid media with the steeper flute angle toward the air inlet.

Next step: Get the right size from the pad finder.

4 Check the belt and bearings

UA Extension says the belt should give about 1/2" when pressed. MasterCool specifies about 3/4" deflection under 3 lb of force on its units, so use your manual's number. PNNL and UA Extension both say to lubricate the bearings if your model calls for it.

Next step: Write down your belt size while you're there, in case you need a spare.

5 Reconnect water and set the float

Reconnect the water line and let the pan fill. UA Extension says the water level should sit about 1" below the top of the tray. PNNL says to make sure the float works properly. MasterCool warns: "Do not connect the water supply to any soft water applications."

Next step: Look for drips at the fittings before you close the panels.

6 Run the pump and check the pads soak evenly

Run the pump alone and watch the pads. UA Extension says to check that they saturate evenly and to look for leaks. Dry streaks usually point to clogged distribution holes or nozzles.

Next step: If pads stay dry in spots, see step 7, then the pad replacement signs.

7 Clear the nozzles or distribution holes

PNNL says to check that water nozzles are aimed to saturate the pads and to clean them with vinegar to remove calcification. Albuquerque's water ranges from "moderately hard to hard" (ABCWUA), so scale builds up here.

Next step: If you have a bleed-off line, check it too. MasterCool suggests starting at 1–2 gallons per hour.

8 Open an exhaust path and test

The cooler needs somewhere to push air: about 2 sq ft of open window or relief vent per 1,000 CFM (PNNL, citing PG&E). UA Extension also suggests running the pump a few minutes before the fan so the pads are wet first.

Next step: Find the opening size for your cooler with the calculator. If something isn't working, request a free quote.

Sources

Published October 30, 2026. These are general tips; follow your cooler's manual where it differs.

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