Final answer:
Excessive water pressure is the primary cause of water-spill accidents, as it can lead to the failure of plumbing fixtures.
Step-by-step explanation:
A primary cause of water-spill accidents is excessive water pressure. When the water pressure in a system becomes too high, it can lead to failures in plumbing fixtures, causing them to leak or burst and resulting in water spills. This concept is related to the principles of fluid dynamics, where high pressure can overcome the resistance in pipes and connections, leading to malfunctions.
Low or decreased water pressure can cause inconvenience and indicate a problem in the water supply system, but it is typically not the cause of water spillage accidents. Moderate water pressure is usually the desired state for proper functioning of water systems without accidents. Excessive water pressure, however, stands out as the primary cause that would likely lead to such incidents.