Coming out of the bottom of a panel and into the ground, you would either have to run EMT, then convert to metal ridgid in the ground until it reaches 18" then convert to PVC. Or could we just run PVC all the way from the panel down to the ground and to the load?, if so, it seems we could stay at 6", or would it have to go to 18".
Or PVC from the panel to metal ridgid then back to PVC at 18"? All Schedule 80 Ridgid PVC if course. UMM..
The Golden Rule - "The man with the gold makes the rule"