Calculating GPM from Pipe Size and Pressure

Flow Rate Formulas:

\[ V = \sqrt{\frac{2 \times (P_1 - P_2) \times 144}{\rho}} \] \[ Q = V \times A \times 448.83 \]

Inlet Pressure (P₁):

psi

Outlet Pressure (P₂):

psi

Fluid Density (ρ):

lb/ft³

Pipe Diameter:

inches

Velocity (V): ft/s

Flow Rate (Q): GPM

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1. What is GPM from Pipe Size and Pressure Calculator?

Definition: This calculator estimates the flow rate (in gallons per minute) through a pipe based on pressure difference and pipe diameter.

Purpose: It helps engineers, plumbers, and fluid system designers determine flow rates in piping systems.

2. How Does the Calculator Work?

The calculator uses two main formulas:

\[ V = \sqrt{\frac{2 \times (P_1 - P_2) \times 144}{\rho}} \] \[ Q = V \times A \times 448.83 \]

Where:

\( V \) — Velocity (feet per second)
\( P_1 \) — Inlet pressure (psi)
\( P_2 \) — Outlet pressure (psi)
\( \rho \) — Fluid density (pounds per cubic foot)
\( Q \) — Flow rate (gallons per minute)
\( A \) — Cross-sectional area of pipe (square feet)

Explanation: The pressure difference is converted to velocity, which is then multiplied by pipe area to get volumetric flow rate.

3. Importance of Flow Rate Calculation

Details: Accurate flow rate estimation ensures proper system design, pump sizing, and meets process requirements in fluid systems.

4. Using the Calculator

Tips: Enter the pressure values (P₁ > P₂), fluid density (default 62.4 lb/ft³ for water), and pipe diameter in inches. All values must be positive.

5. Frequently Asked Questions (FAQ)

Q1: What's the 144 factor in the equation?
A: This converts psi (lb/in²) to lb/ft² (1 ft² = 144 in²).

Q2: Why 448.83 in the flow rate formula?
A: This converts ft³/s to GPM (1 ft³/s = 448.83 GPM).

Q3: What's a typical fluid density?
A: Water is 62.4 lb/ft³ at room temperature. Oil is about 55 lb/ft³, seawater about 64 lb/ft³.

Q4: Does this account for friction losses?
A: No, this is theoretical maximum flow. Actual flow will be less due to pipe friction and fittings.

Q5: What pipe diameter range is this valid for?
A: This works for all diameters, but assumes turbulent flow which is typical for most practical applications.