I'm replacing the solid HDPE drain pipes in my back yard because they
are full of ficus roots, and I have several questions:
1) The root invasion was apparently invited by leakage at the pipe
joints. The pipes were just shoved into the couplings, which I guess
is typical with HDPE. Is there any way to keep the roots out in the
future, maybe some way to seal the joints or otherwise leak-proof
them?
2) I've seen perforated pipes for lawn drainage. Why would you want to
use these instead of solid pipe of the same material?
3) I have one existing pipe that is not infiltrated and drains to the
street via a hole in the side of the curb. I want to tap a new drain
pipe into this one (running perpendicular to it), but since the pipe
is already fixed in place I can't just cut out a section of it and
attach a tee there. The only thing I can think of is to cut a hole in
the existing pipe and somehow connect the end of the new one to the
hole. Any ideas about fittings or materials to make this connection?

Thanks for any help on any of these questions.

BF