Final answer:
A drop in water pressure opens a special dry pipe valve, usually related to increased use and resistance in the water main supplying multiple households.
Step-by-step explanation:
The drop in water pressure causes a special dry pipe valve to open. This phenomenon is closely linked to flow and resistance, which can cause changes in pressure within your home's water supply system. Specifically, during heavy use on hot summer days, many households may draw water from the same water main, creating increased flow and resistance and leading to a notable drop in pressure. To prevent damage or unintended operation within sprinkler systems, a dry pipe valve will open to maintain the system's integrity when it detects a significant pressure drop.