Should top of Drainage Chambers be Level ?

[Spinny]

Just wondered are the tops of drainage chambers supposed to sit level if you put a spirit level on them in both directions - I  mean across the chamber itself rather than the cover ?

Just thinking presumably they are made with slight angles/falls on the outlets/inlets. so designed to sit square at the top ?

[Mr Punter]

spirit level accuracy not required but obvs the fall must be in the correct direction.