Add a few drops of lubricant or water-displacing spray around the threads of the bolt and nut.
Hold the head of the bolt with a wrench.
Grasp the nut with the pliers.
Turn the bolt counter-clockwise while holding the pliers steady, until the bolt comes free.
Brace the pipe by having an assistant help you, or holding it on the ground with your body weight.
Tap the bolt with the hammer, using enough force to move it.
Hit the sides of the bolt with the hammer to move the bolt back and forth in the hole.
Continue hitting the hammer back and forth and on the top until it pops through the hole. You will have to retrieve it from inside the pipe.