Demand variations in urban water supply:\r What is the typical ratio of maximum daily consumption to average daily demand used for design checks?

Introduction / Context:
Water demand fluctuates hourly, daily, seasonally, and with special events. Designers apply peaking factors to ensure the system can meet short-term high demands without unacceptable pressure drops. One common metric is the ratio of the maximum day to the average day demand.

Given Data / Assumptions:

• Typical medium-to-large city with mixed residential, commercial, and institutional use.
• Historic practice and textbook design values are acceptable for preliminary sizing.
• Fire flow is handled as a separate, concurrent check.

Concept / Approach:
Empirical peaking factors reflect user behavior and climate. Many standards employ a maximum-day-to-average-day factor between 1.6 and 2.0. In numerous exam syllabi and design examples, 1.8 is adopted as a representative value for conservative planning at the concept stage.

Step-by-Step Solution:
Identify the parameter: Max Day / Average Day.Compare listed ratios to typical guideline range.Select 1.8 as a standard, commonly used design factor in teaching practice.

Verification / Alternative check:
Utility demand records often show 60–100% increase on peak days relative to annual average, supporting factors near 1.8 for preliminary sizing before detailed modeling.

Why Other Options Are Wrong:

• 1.0 implies no peaking and is unrealistic.
• 1.2 and 1.4 are low for many climates/behaviors.
• 1.6 can be used, but 1.8 is more typical for conservative designs in many texts.

Common Pitfalls:

• Confusing maximum day factor with maximum hour factor; the latter is higher.
• Ignoring concurrent fire flow checks which can govern main sizing even if peaking factors are satisfied.

Final Answer:
1.8