Swamp cooler pump not pumping: how to tell a dead pump from a packed screen in Reno

A swamp cooler pump that is not pumping is either dead, starved, or blocked, and the difference is worth two minutes on the roof before anyone buys a part. A packed inlet screen costs nothing to fix and looks exactly like a dead pump. A pump that has seized from scale or burned from running dry is $150 to $400 installed, sized to the cooler. A pump that runs while the pads stay dry is a distribution problem, not a pump problem. Send a photo of the pan with the pump and float visible and the tech can usually tell which from the picture.

Check this first (two minutes)

1. Pump-only mode. Set the cooler to pump only and listen at the pan. A hum means the pump has power; silence means the receptacle, the switch, or the pump’s own winding.
2. Lift the pump out. Unplug it inside the cooler, lift it out of the pan, and look at the inlet screen or basket. A screen packed with scale, aspen fibers, and grit is the most common “dead pump” in Reno, and it rinses clean.
3. Spin the impeller. With the screen off, the impeller should turn freely by hand. Locked solid is scale, and a scaled impeller sometimes frees up after a soak, but it will lock again.
4. Check the pan level. A pan that is empty or nearly so means the float shut the water off and the pump has been running dry; that pump is likely cooked even if it hums.
5. Look at the tubes. If the pump runs and water reaches the trough but the pads are dry in patches, the spider or distribution tubes are clogged. Different fix.

What is usually wrong

Every number is from the pricing page, and the pump and float page explains the sizing.

Why Reno pumps fail

Scale, and a supply that swings. The Truckee Meadows Water Authority draws from the Truckee River and treats it at Chalk Bluff and Glendale, and river water is soft: 2 to 5 grains per gallon in most of Reno and Sparks by TMWA’s own area reports. But the number swings wide by area and by quarter, from 1.8 grains in North Reno up to 13.9 in Southwest Reno in the first quarter of 2026 and 10.4 in West Reno, and TMWA says the groundwater wells it runs from mid-April through October can and do change the water chemistry somewhat. A cooler evaporates hundreds of gallons a season and leaves every grain of mineral in the pan. That crust grows on the impeller and plugs the screen. A bleed-off line that dumps a little pan water continuously is what keeps the concentration down, and it gets set with any pump replacement.

Dry running. A float valve that sticks closed leaves the pan empty, and a submersible pump without water around it overheats in minutes. This is how a $150 float failure becomes a $400 pump failure, and it is why the float gets set with every new pump.

Freeze. A pump left in a full pan into the first fall freeze, which NOAA’s normals put at October 19 as the 50 percent date at the airport and October 5 in Sparks, gets its housing cracked. It hums fine in April and leaks from the seam. The fall winterization lifts the pump out and drains it for exactly this reason.

What the replacement includes

The pump is matched to the cooler’s CFM by GPH rating, because an undersized pump leaves the top of the pads dry and an oversized one floods the pan and the roof. The pan gets cleaned while the pump is out, the inlet screen gets checked, the float gets set to the fill line, the distribution tubes get cleared, and the bleed-off gets set. A pump dropped into a dirty pan with a stuck float is a repeat call by August.

What to expect on the call

Say whether the pump hums or is silent, and whether the pan has water in it. Send a photo of the pan with the pump and float visible. The tech arrives with pumps and floats for the common sizes, checks the screen and the receptacle before replacing anything, and confirms the part price before it goes in.