Empirical formulas for estimating fire demand in water supply design:\r Which named empirical relationship is commonly cited for calculating a city’s required fire demand?

Introduction / Context:
Water supply systems must provide adequate fire flow in addition to domestic and industrial demands. Designers often reference empirical formulas derived from historical fire fighting needs and urban densities to estimate the required fire demand quickly. This question checks familiarity with the commonly cited named formulas.

Given Data / Assumptions:

• Urban area requires a planning value for peak fire flow.
• Empirical formula usage is acceptable at predesign or where detailed risk studies are unavailable.
• The choices list well-known named relationships.

Concept / Approach:
Several formulas exist: Kuichling, Freeman, and the National Board of Fire Underwriters (often shortened to “Underwriters”) are among the most frequently mentioned in traditional syllabi. While local codes ultimately govern, the Underwriters formula is widely recognized and historically used to set conservative fire demand values as a function of population or built-up area characteristics.

Step-by-Step Solution:
Identify the intent: pick a widely known empirical fire demand relationship.Among common choices, the Underwriters formula is a benchmark reference in many manuals and exam contexts.Select Underwriters formula as the best answer to the phrasing “commonly cited”.

Verification / Alternative check:
Textbooks on water supply engineering routinely describe multiple formulas but frequently demonstrate examples using the Underwriters expression due to its prevalence in older North American standards and its conservative nature.

Why Other Options Are Wrong:

• Kuichling's and Freeman formulas are also used but are less universally referenced in many foundational examples compared with Underwriters.
• Buston's formula appears in some references but is less common in standard design problems.
• “None of these” is incorrect because recognized formulas do exist.

Common Pitfalls:

• Treating any single empirical formula as universally applicable without checking local fire code requirements and risk assessments.
• Confusing the population parameter form (e.g., use of square root of population) between different formulas.

Final Answer:
Underwriters formula