Are you talking about minerals etc from the water, or all the junk that breaks away from the pads?
Our water isn't bad, very little stuff from that. I do get some pad material, but I always clean it out, then drain it and dry everything before covering the cooler for the winter. In the spring I usually just oil the bearing blocks and turn the water on, and it's good to go.
junk that builds up in my'n is rust, calcium, dirt, cause its windy in winter time, shingle rocks :
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