I finally talked my mom and stepdad into drip irrigation. I was installing their system today, and I noticed that the fittings are different now. The design of the fittings that attach to the header line through a punch hole now includes a threaded piece on the header line side that can be screwed down to tighten the fitting against the header line. It's a great improvement. Mine have always leaked.
Here is the old style:
The left side goes into the punched hole in the poly tubing that is the header line. That's where mine always leaked.
Here is the improved version:
Notice the threaded piece on the left. That screws down to hold the fitting tightly in the header line.
I'm going to replace all of mine next season with the improved style. It is a much better design.