I use an evaporative bong cooler with a shower head close to the top of a 3 inch pipe. I put a sponge on top of the showerhead where the 2 return lines come in. I then added an elbow to the 3 inch pipe, so it points into a sunny window. The black plastic pipe warms up and warms the sponge helping evaporation. I am losing more water now, but the water stays cooler. And if the sponge stinks you take it out and rinse with bleach and then it's all good again. I tried using a sponge inside the pipe and it did not work well for me.
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