Complex sentence: Named in the time period when drainpipes were made from terracotta tiles, the modern material is typically a length of plastic pipe with small slits or weep holes in it, which is buried surrounded by aggregate larger than the slits.
Split into simpler sentences: Named in the time period when terracotta tiles were typical for drain pipes, the modern material is typically plastic pipe with small slits or weep holes in it. It is buried surrounded by aggregate larger than the slits.