Scott Townsend wrote:
every 20'???

Hmmm... Seems Excessive? We were thinking of one right at the exit
of the home, then its pretty much a straight shot to the tank. Would look
funny with 4 cleanouts sprinkled throughout the yard?

Set a Bar-B-Que on the first, a rock garden on the second, and a bird-bath
on the third.

You'll have a hard time going eighty feed with a fifty-foot snake.