What can improper installation of drainage planes lead to?

Improper installation of drainage planes can significantly increase the risk of flooding. Drainage planes are designed to redirect water away from structures and ensure effective water management. When these planes are not correctly installed, water can accumulate in areas it shouldn't, leading to potential flooding and water damage. This can create serious issues within a building, including undermining the foundation, leading to mold growth, and damaging interior furnishings and finishes.

In contrast, the other choices do not align with the consequences of improper drainage plane installation. Decreased energy costs and enhanced plumbing performance are benefits associated with proper installation and functioning systems. Similarly, longer appliance lifespans would be a result of adequate water management and maintenance, rather than stemming from improper installation, which could actually lead to appliance damage due to water exposure.