A Double Check Back-flow assembly provides protection against which of the following?

A Double Check Back-flow assembly is specifically designed to protect against back-siphonage and back-pressure from pollutional hazards within a water distribution system. This type of assembly consists of two check valves that work to prevent contaminated water from flowing back into the clean water supply, thereby safeguarding public health.

Back-siphonage occurs when there is a negative pressure in the potable water system, which can potentially draw contaminants from a source into the clean water supply. Back-pressure can occur when there is an increase in water pressure on the contaminated side of the assembly, causing the contaminated water to be forced back into the safe water supply.

The distinctive capability of a Double Check Back-flow assembly lies in its ability to address both scenarios concerning pollutional hazards. This quality makes it particularly suitable for applications where there is a chance that non-potable water could mix with the potable water system due to pressure fluctuations or the back-siphonage phenomenon.

In contrast, other options such as electrical hazards or flooding of storage tanks do not pertain directly to the back-flow protection functions an assembly provides, highlighting the focused role of the Double Check Back-flow assembly in maintaining water quality and safety.