Common sources of contamination in cold water supplies and how can they be mitigated?

• A. Cross-connections with non-potable sources; mitigated by backflow prevention
• B. Painting pipes to protect from contamination
• C. Installing more storage tanks
• D. Using larger pipe diameters to dilute contaminants

Answer: (A)

The main idea tested is how contamination can enter a cold water supply and how backflow prevention stops it. Cross-connections with non-potable sources create a pathway for contaminants to flow back into the potable system if pressure drops, leading to tainted drinking water. The best mitigation is backflow prevention: properly installed and maintained devices (such as backflow preventers and air gaps) that stop reverse flow and protect the distribution from back-siphonage or backpressure. Regular testing and correct siting of these devices are essential to keep the system safe.

Painting pipes doesn’t address the risk of backflow or cross-connections, so it doesn’t mitigate contamination. Installing more storage tanks can add volume but doesn’t prevent backflow and can introduce stagnation or contamination if not properly sealed and managed. Using larger pipe diameters to dilute contaminants is not a valid protective measure; dilution doesn’t eliminate contamination and can mask a problem rather than resolve it.