Final answer:
For water to drain effectively from a house's waste systems, adequate venting is necessary to allow for proper airflow, prevent vacuum scenarios, and facilitate the expulsion of sewer gases.
Step-by-step explanation:
For water to drain freely out of the house waste systems, there must be adequate venting. Venting is essential in a drainage system because it allows air to enter the pipes, ensuring that water flows smoothly and prevents vacuum situations that could disrupt the flow of water. Venting also helps to expel sewer gases and maintains the proper balance of air pressure in the waste system, which facilitates the free flow of wastewater without blockages.
Without proper venting, the movement of wastewater is hindered, leading to slow drainage, gurgling sounds, and the potential for traps to be siphoned, allowing sewer gases to enter the home. Traps themselves are critical components that prevent sewer gases from coming back into the house, but they require appropriate venting to work effectively. Therefore, the correct answer is C. Venting.