loretta: I just did this from my barn to my pond. My shingled roof is pretty old, so there is no grit. I have no idea if it will make a difference (my pond volume is 3.35 acre-ft), but I guess every little bit helps.

The downside is that I had to invest in 300 ft of 4" corregated drain pipe. Some I bought new, some I bought used through Facebook Marketplace. This pipe is the most economical for long runs.

I will get around to burying it someday.

[Linked Image from i.imgur.com]