Question

When a house's drainpipes are backed up from tree roots, homeowners can blame which plant characteristic?

Answer 1

hydro-tropism

Explanation:

Plants are very good at finding sunlight, water, and the surface. They have a host of tropisms such as phototropism, gravitropism and specifically hydro-tropism is the one at fault here. Plant roots will find moisture and grow in that direction, and drainpipes are a water source.

If we want to be pedantic, your pipes would already have to be leaky but hydro-tropism is the concept anyhow.