That's interesting as I have to put in new water line a couple hundred feet. I stopped and asked an operator how that directional drill worked. He explained but I still don't understand. How it's guided, how one knows where it is? How they then can pull in pipe?
I never understood it either until I saw it the other day. The tip has a small flat plate on the end mounted at an angle. The tip is connected to pipe through which water is pumped. The water really does the boring as it is very high pressure and jets out the end and machine just pushes the tip forward (it does not spin to "bore" the hole, most of the time it just pushed through the soil unless it is really hard). Since the connection back to the machine is rigid spring steel pipe they know the angle to the tip and it is shown on a screen in front of the operator. So to change directions they rotate the tip so that the angled plate changes the direction of the boring action. Of course they have to stop the length of a pipe section and add another pipe but that is quick. they went 100' on my property in about 6 minutes.
The tip also has a magnet in it and they have a box that a guy walks along and can tell the location and depth of the tip at any time. This is also transmitted back to the operator's screen so he has the information. they cannot change direction very quickly, i.e. about 10 degrees per ten foot so a 90 degree turn has about a 90' radius.
Once they have bored through they unscrew the boring tip and put on a unit that has mesh wire that are like chinese finger locks. these slide over the capped end of the tubing you are going to use. then they start retracting the boring machine and somebody has to feed the out of the coil into the hole so it does not kink and they pull it back through removing sections of pipe as they go. When they are done retracting they have the pipe through. In my case they pulled a 3/4" water line, a 3/4' gas line, and a tracer wire.
In my case we had to turn a fairly sharp corner for the last 15' into my house and they dug a quick trench for that end of it with the mini-ex and intersected where the lines were (the directional boring machine had to start back a little so that it had a certain length to get to depth). The lines had been pulled out where the boring machine went in so once they had broken through the intersection of the trench and where the lines were one guy was there and the other was at other end of the lines and he pulled them back into the hole until the ends got to the intersection and then they pulled them through the trench. The hole is larger than the tubes and is muddy from the water that is constantly being injected as the tip bores so you can pull 3-400' of line no problem.
The tricks in all of this are:
1) Knowing how to operate the machine and to pay attention as to where the tip is as it is going so that it:
a) goes to the right end point
b) you know where to dig to for the intersection point
2) Knowing how to dig the intersection point without nicking the lines
3) Having people who pay attention so that you do not pull the lines back to far when trying to get the ends to the intersection.
All i had left was a little mess on each end from digging out the dirt and a little hole with some mud around it in my lawn where they had set up the machine. There were also some track marks as the soil was a little moist and where those tracks turn it ripped up some grass.
