Using a water pipe for a ground is no longer part of the NEC. This is because many houses have their water from a well or municipal system plumbed into the house with HDPE plastic pipe - so as soon as the water line gets outside the house, it is no longer a conductor of electricity. 

The ground at your entry box should be the ground for the house. This should consist of two ground rods, driven into the ground, set about 6 to 8' apart, bonded together with #6 wire, and then up into the entry panel with #6 wire. 

As for finding your shock point: You could use a "chicken stick" - a glowing-tip live wire tester. They're available at Home Depot and other well stocked hardware stores. You just touch the tip to a conductor and if it lights up the LED, then there's at least 90 volts present.