Commercial Drain Sizing Calculator
Size commercial drain, vent, and cleanout requirements based on fixture units and building configuration.
Inputs
Results
Drain Pipe Size
4 in
Vent Pipe Size
2 in
How to Use This Calculator
- Enter Total Fixture Units (DFU), Building Stories, and Pipe Run Length (ft).
- Review Drain Pipe Size and Vent Pipe Size (in).
- Use Cleanouts Required and Required Slope (in/ft) to inform your decision.
- Use the chart to visualize the results and explore different scenarios by adjusting inputs.
What each input means
- Total Fixture Units (DFU)
- Sum of drainage fixture units from all connected fixtures (per UPC/IPC table)
- Building Stories
- Number of stories in the building — affects stack sizing
- Pipe Run Length (ft)
- Total horizontal pipe run length from most remote fixture to building sewer
How this is calculated
Worked example, using the default values
- Identify Input ParametersTotal Fixture Units (DFU) = 60, Building Stories = 3, Pipe Run Length (ft) = 150 = 3 input(s) provided
- Calculate Drain Pipe Size4 = 4
- Calculate Vent Pipe SizeVent Pipe Size2 = 2
- Calculate Cleanouts RequiredCleanouts Required4 = 4
Engine last updated . Checked against 2 independently-derived tests — how we verify calculators.
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