I'm trying to look up if there is a length.. I know that the tank needs to be a minimum of 10 feet from the house/dwelling.
According to one source, the outlet should be at least two inches lower than the inlet. Inside the tank there should be at least a four inch space between the end of the inlet pipe and the concrete baffle. But that source was from 1982. I'm searching for something more recent.
I don't know about the pipe lengths. Hopefully someone who knows for sure can respond.