I buried corrugated for my downspouts. Rented a trencher to bury a phone line and did the downspout drains at the same time. I purchased corrugated black pipe in a 100' roll. Went down about 18" by the house and took it into the woods at about 3". Built a shallow drywell at the outlet end with small stones so I didn't get wash out. Works real well. Not as fancy as some have done, but functional.