Why is this earth rod installed?
There's a thing. The tank is plastic and raised off the ground. The oil pipe is covered in plastic so normally is not an extraneous-conductive-part. But the earth rod makes it an extraneous-conductive-part thus it needs bonding. So now the P.M.E. earth is exported to the outside pipe. Is that good? A lost neutral may raise the metal pipe up to mains Voltage and anyone touching it at the oil filter position may receive a 
shock. A sideways picture of the oil tank..........
Z.
There's a thing. The tank is plastic and raised off the ground. The oil pipe is covered in plastic so normally is not an extraneous-conductive-part. But the earth rod makes it an extraneous-conductive-part thus it needs bonding. So now the P.M.E. earth is exported to the outside pipe. Is that good? A lost neutral may raise the metal pipe up to mains Voltage and anyone touching it at the oil filter position may receive a shock. A sideways picture of the oil tank..........
Z.