What is backflow in a cold water system and why is it a concern?

• A. Backflow is the unwanted reverse flow of water into the clean water supply, potentially carrying contaminants.
• B. Backflow is a type of pipe corrosion process.
• C. Backflow is a method to increase water pressure.
• D. Backflow is a process of removing contaminants.

Answer: (B)

Backflow is the unwanted reverse flow of water into the clean drinking-water supply. It happens when pressure in the potable system drops or when a siphon pulls water from a connected but non-potable source back toward the main supply. The danger is that contaminants from irrigation systems, fertilizers, chemicals, wastewater, or dirty hoses can be drawn into the drinking water, creating health and safety risks. Because of that, plumbing rules require devices or setups that prevent reverse flow, such as backflow preventers and air gaps, to keep the clean supply protected even when pressures change or a non-potable source is connected.