No one with a sprinkler system wants to see water coming out of the ground in the wrong place. It seems that anything stuck into the ground has an unusual attraction to the water pipes running under the surface. If you're the least bit handy, you don't have to call the irrigation company--and wait for them to get around to you--to repair a sprinkler system puncture.
Shut the water off to the line that is leaking and dig where the water was coming out of the ground. Work carefully. Don't create more work for yourself by breaking the pipe further.
Expose 6 to 8 inches of pipe to either side of the puncture and give yourself about 8 to 10 inches of room to either side of the pipe, and about 6 inches below the pipe.
Cut the broken section of pipe out with the hacksaw. Make sure you cut out all the damage. Splits can sometimes run parallel with the pipe for quite some distance. Leave yourself at least 3 inches of pipe exposed from the sides of the hole on both sides. Make your hole larger if necessary, but keep it as small as possible so the lawn can recover sooner.
Determine the type and size of pipe. Irrigation systems are usually installed with either flexible water pipe or rigid PVC pipe. It's pretty simple: Flexible water pipe is black and PVC is white. Size is tricky, though. One-inch pipe doesn't measure exactly 1 inch inside or outside. The reasons are complicated and not worth your time to figure out. The simplest way to make sure you get what you need is to take the cut-out piece of broken pipe with you to the store.
Buy four 90-degree elbows that match your pipe. Get barbed fittings for flexible water pipe or glue fittings for PVC. You'll also need a piece of matching pipe about a foot longer than the length of the piece you cut out. Some stores offer short sections of pipe--2 to 5 feet--for repairs. Others offer full sections only, so it pays to shop around. You'll need eight hose clamps for a flexible pipe repair or a bottle each of primer and glue for a PVC job.
Dry fit an elbow on the two cut ends of your pipe. If your pipe is sufficiently deep, orient the open ends of the elbows straight up. If the pipe is already dangerously close to the surface, orient them to one side.
Cut two small sections of pipe just a fraction longer than needed for two fittings. For example, using 1-inch PVC, each fitting is 1-inch deep, so you need to cut the sections 2 1/2 inches long.
Place the small stubs into the installed elbows. Don't clamp or glue yet. Dry fit the remaining two elbows onto stubs and measure the length of pipe you need to bridge the gap between the two, taking into account the length needed for the fittings. Cut the piece of pipe and dry fit everything together.
Install hose clamps at every fitting on a flexible pipe system and your repair is complete. It's a little trickier on a PVC system. Begin by priming and gluing the elbows onto the two cut ends in the ground, making sure the open ends of the elbows point precisely the same direction--straight up, straight left or straight right. Prime and glue the stubs in place. Prime and glue the remaining two elbows onto the bridge piece. Finally prime and glue the bridge piece and its elbows onto the stubs. The last two glue-ups should be done as quickly as possible--the glue has a very short open time.