Explain the difference between primary distribution and secondary distribution in cold water systems.

• A. Primary distribution runs from the service pipe from the street to the building; secondary distribution is internal branching from the rising main to individual fixtures.
• B. Primary distribution is only for hot water; secondary is for cold water.
• C. Primary distribution applies to irrigation only; secondary to domestic use.
• D. They are identical concepts in the same system.

Answer: (A)

The main idea is that cold water distribution is split into two stages: bringing water into the building, and then distributing it inside to each fixture. Primary distribution covers the water from the street service pipe into the building, ending at the point where the building’s internal distribution starts (typically the rising main or the entry to the cold-water system). Secondary distribution is the internal network that branches from the rising main to feed individual fixtures—sinks, toilets, showers—through branch pipes and valves. This separation helps manage pressure and control: the entry point governs supply into the building, while the internal network handles delivery to each outlet. The other statements mix up concepts (hot water vs cold, irrigation vs domestic use) or claim they’re the same, which doesn’t fit how internal cold-water systems are actually arranged.