The way the cooler works is that water feeds into the base, where a pump sends it up into the top of the cooler to trickle down through the pads. The cooler fan draws air through the pads and out through the front of the cooler, where evaporation (very effectively when your humidity is around 20% or less) cools the room. Because we had not used the cooler for months, we assumed that all of the water left in the pan would have dried up and we could simply start chipping away at it. Imagine our surprise when we hauled the cooler outside and found that there was still water sitting under a crust of calcium buildup.
Lisa removed the water pump and we proceeded to scrape the loose upper layer and mop up the water. We dug out the largest accumulation of calcium build up, then poured in CLR solution and fresh water to try and soak out more of the calcium.
Repeated rounds of scrubbing, scraping, and soaking got more junk out of the bottom of the cooler, but clearly more significant work was needed. We knew there were a few bare spots where the original paint had peeled off, but as we pulled out junk, we could see more bare spots and also rust.
Rust is bad. If left untreated, you eventually end up with a hole that means you need to replace the pan or even the whole cooler.
Lisa figured out how to detach the pan from the upper portion of the cooler, and we set the upper section aside on the back porch.
With all of the superstructure removed, it was much easier to work on the pan, but also it became obvious how much more work was needed.
Our trip over to Fallon a couple of days ago included shopping for both tools and treatments we weren't able to find in Fernley. That was a success, so Lisa got to work.
Among the things we purchased was a high-capacity respirator (to avoid inhaling paint chips and other fine debris) and a grinding wheel (not made in China, which was the challenging part). Lisa donned the mask and appropriate ear and eye protection, attached the grinder to her smaller electric drill (the large heavy duty one we bought for drilling holes in cement is too heavy, both in weight and rated speed for the grinder) and set to grinding off the more stubborn accumulations and the rust and loose paint, taking much of the pan down to bare metal.
After all of the grinding (and brushing and cleaning out the loose debris), Lisa applied several coats of rust treatment (which attacks and seals rust and over which you can paint later). After this cures in another day or so, we can start applying new paint. Swamp coolers are mostly painted in a uniform beige color, and many places sell it in both spray and liquid form.
The piece of paper towel in the middle of the pan is sticking out of the pan's drain plug to keep paint from getting into it and blocking the threads of the drain cover.
We're significantly down the restoration path now. Repainting can start as early as tomorrow as the pan is currently sitting in the sun drying out from the rust-prevention treatment. There will still be rounds of waiting for coats of paint to dry after that, but when that's done, we should be able to reassemble the cooler and get it working again.