GPM to PSI Conversion Relationship
The pressure loss (PSI) due to flow rate (GPM) in a pipe can be calculated using the Hazen-Williams formula:
P = \( \frac{4.52 \times Q^{1.85} \times L}{C^{1.85} \times D^{4.87}} \)
Where:
- P = Pressure loss (PSI)
- Q = Flow rate (GPM)
- L = Pipe length (ft)
- C = Hazen-Williams coefficient (material-dependent)
- D = Pipe diameter (in)
Input Parameters:
- Flow Rate: Volume of fluid per unit time (e.g., GPM, L/min).
- Pipe Length: Length of the pipe (ft or m).
- Pipe Diameter: Inner diameter of the pipe (in or mm).
- Hazen-Williams Coefficient (C): Depends on pipe material:
- Asbestos-cement: 140
- Cast iron new: 130
- Cast iron 10 years: 113
- Cast iron 20 years: 100
- Cement-Mortar Lined Ductile Iron: 140
- Concrete: 140
- Copper: 140
- Steel: 120
- Galvanized iron: 120
- Polyethylene: 140
- Polyvinyl chloride (PVC): 150
- Fibre-reinforced plastic (FRP): 150
- Custom: User-defined (50-200)
Practical Applications
This calculator is useful in:
- Plumbing: Estimate pressure drop in water supply lines.
- Irrigation: Calculate pressure loss for sprinkler systems.
- Engineering: Design piping systems with acceptable pressure losses.
Example Calculation
If the flow rate is 0.01 GPM, pipe length is 10 ft, diameter is 4 in, and material is PVC (C = 150):
P = \( \frac{4.52 \times 0.01^{1.85} \times 10}{150^{1.85} \times 4^{4.87}} \) ≈ 0.000013 PSI
Displayed as: 1.30E-5 PSI
Similarly:
- bar ≈ 8.96E-7 bar
- kPa ≈ 8.96E-5 kPa
Conversion Constants
Key conversion factors:
- 1 Gallon = 3.785411784 Liters
- 1 ft = 0.3048 m
- 1 in = 25.4 mm
- 1 PSI = 0.0689475729 bar = 6.89475729 kPa
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