Where is a backflow preventer typically installed in relation to the water meter in a domestic cold water system?

• A. On the building side of the water meter or at a protected cross-connection near the point of entry.
• B. Inside the main meter housing.
• C. After the furthest fixture.
• D. On the street side of the meter.

Answer: (A)

The main idea is to protect the public water supply by stopping any reverse flow as water enters the building. A backflow preventer is placed at or near the point where the water enters the building, i.e., on the building side of the water meter or at a protected cross-connection right at that entry. This location keeps the entire internal plumbing protected from backflow and is the most effective way to prevent contaminants from being drawn back into the supply.

If the device were located after the furthest fixture, backflow could still occur back toward the main or through internal cross-connections, defeating protection of the supply. Placing it inside the meter housing isn’t a typical or practical installation, and placing it on the street side of the meter would leave the building’s internal system unprotected. Thus, installing on the building side of the meter—or at the point of entry—is the standard approach.