I recently installed a 30 amp 2 pole circuit breaker using 10/2 w/ground for a new dryer. At the box, I wired the 10/2 w/ground black to one side and the white to one side of the 30 amp 2 poled breaker and the ground to the side bar for ground.

I also installed a three prong receptacle, wiring the black and white to each top of the "Y" and the ground to the bottom of the "Y". I ran a piece of copper wire from the recptacle box to a cold water copper pipe for grounding purposes.

Does this sound safe or should I have used 10/3 w/ground ?

Should have used #10-3 with ground.

Both using #10-2 and grounding to the water pipe are illegal and violates the National Electric Code.