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Calcimator

Drainage Fixture Unit Calculator

Calculate total drainage fixture units and determine required drain, vent, and stack pipe sizes per plumbing code.

Inputs

IPC Table 709.1: water closet = 4 DFU; urinal = 4 DFU per IPC fixture unit table

IPC Table 709.1: lavatory = 1 DFU; kitchen sink = 2 DFU; service sink = 3 DFU

IPC Table 709.1: shower = 2 DFU; requires 2" minimum trap and 2" drain per IPC

IPC Table 709.1: bathtub = 2 DFU; combination tub/shower = 2 DFU; requires 1.5" trap

IPC Table 709.1: clothes washer = 3 DFU; requires 2" standpipe and air gap per IPC 802

Results

Total DFU

22 DFU

Required Drain Size

4 inches

Required Vent Size2 inches
Stack Size3 inches
How to Use This Calculator
  1. Count each fixture type in the building: toilets, sinks, showers, bathtubs, clothes washers, and dishwashers.
  2. The calculator sums up the Total DFU using IPC/UPC fixture unit values for each type.
  3. Review Required Drain Size and Required Vent Size to specify pipe diameters on your plans.
  4. Check Stack Size to size the vertical drain/soil stack serving multiple floors.
  5. Use these results to verify your plumbing plans meet code before permit submittal.
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