Had a simular problem a while back. Found that some one had rep-aired a leak with PVC pipe 3' outside of the water entrance to the house. Also the neutral connection at the weatherhead was rusty.
Drove two ground rods and reterminated all the weatherhead connections. This brought a measured 40 volts on the spigots to 1.5 volts. 1 additional ground rod did nothing. Grounding the gas fired water heater did nothing.
Customer was satisfied that the shocks stopped and paid the bill. Recomended that he have the PVC replaced with copper but they have yet to do so. They do not want to see thier flower bed torn up.
Some timesx we cannot fix the real problem so we do the best we can.
Good luck
