During rainy season my crawspace usually have several puddles of water.
Since there is no visible leak, I assume this is from rain water seeping
through the lawn and then into the foundation. The puddles are no more than
1.5 inches deep and are not usually visible at a glance because black
plastic sheets cover the entire crawlspace they tend to float on top of the
puddles.

At one corner of the crawlspace is a 1-foot long, 4-inch diameter black
plastic pipe with a cap that leads outside the foundation. This pipe is at
the end of what looks like a man-made water channel. I assume this is a
water drain. There is no puddle around this area.

The house is built in 1985, is there a code that mandates a crawlspace
drain? I'm wondering if I need to do something about the puddles or if it's
ok as long as they don't get worse.