What is the purpose of a backflow preventer in a hydronic system?

The primary purpose of a backflow preventer in a hydronic system is to prevent contaminated water from returning to the potable water supply. This device ensures that if there is a drop in water pressure within the system, potentially contaminated water does not flow back into the clean water lines. By maintaining a one-way flow of water, the backflow preventer protects public health by keeping the drinking water safe from contamination that could occur due to back siphonage or backflow.

This functionality is critical in any hydronic system to ensure compliance with health and safety regulations regarding potable water. The other choices, while related to hydronic system functions, do not accurately capture the essential role that a backflow preventer plays in preventing contamination.