1. What is a Gravity Drain Flow Rate Calculator?

Definition: This calculator estimates the flow rate of water through a drain or orifice under the influence of gravity.

Purpose: It helps engineers, plumbers, and designers determine the expected flow rate for drainage systems, spillways, and other gravity-fed water systems.

2. How Does the Calculator Work?

The calculator uses Torricelli's formula:

Where:

• \( Q \) — Flow rate (cubic meters per second)
• \( A \) — Cross-sectional area of the opening (square meters)
• \( g \) — Acceleration due to gravity (9.81 m/s² on Earth)
• \( h \) — Height of water above the opening (meters)

Explanation: The formula calculates the theoretical maximum flow rate under ideal conditions, assuming no friction losses.

3. Importance of Flow Rate Calculation

Details: Accurate flow rate estimation ensures proper drainage system design, prevents overflow, and helps in sizing pipes and channels correctly.

4. Using the Calculator

Tips: Enter the cross-sectional area of the drain, height of water above it, and gravity value (default 9.81 m/s²). All values must be > 0.

5. Frequently Asked Questions (FAQ)

Q1: What affects the actual flow rate compared to this calculation?
A: Friction losses, pipe roughness, turbulence, and viscosity can reduce actual flow rates by 10-40%.

Q2: How do I measure the cross-sectional area?
A: For circular pipes: \( A = \pi \times r² \). For rectangular channels: \( A = width \times height \).

Q3: What if my drain isn't full of water?
A: Use the actual water height (h) from the drain opening to the water surface.

Q4: Can I use this for other liquids besides water?
A: The formula works for ideal fluids. For viscous liquids, additional factors must be considered.

Q5: How do I convert the result to other units?
A: 1 m³/s = 1000 liters/second = 15850 gallons/minute (US).