Single-family residences are most commonly served with which service line size?

• A. 1/2 inch
• B. 1 inch
• C. 1 1/2 inch
• D. 3/4 inch

Answer: (D)

The situation tests typical residential service line sizing based on balancing adequate flow with reasonable cost. For a single-family home, a 3/4 inch service line is large enough to deliver enough water for usual peak demands (multiple fixtures in use at once) without causing excessive pressure drop, yet not so large that installation costs and material waste become unnecessary. A 1/2 inch line can restrict flow significantly when several fixtures are used simultaneously, leading to noticeable pressure loss. A 1 inch or larger line provides more flow but is generally unnecessary for a standard home and adds unnecessary expense. Therefore, 3/4 inch is the most common, practical choice for single-family residences.