Stormin Mormon wrote:
I saw that drain blower, from Johnstone. The cartridges are
about two bucks each. But, it's a lot lighter than an air
compressor. I could much more easily carry it up the ladder,
also.

My plan at the moment is to use small compressor, length of
air hose, and a blow gun. Stick the blow gun into the clean
out, wrap with a towel, and squeeze the handle. Some of the
air will of course blow into the pan. But, much should blow
down the length of the drain. The drain is huge.

I'm wondering if wasps have nested in the open end. Need a
big nylon sock or something to keep the wasps out.

Not with a constant trickle of water. Unless they're waterfall wasps (only
found in Micronesia and Vermont).