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Calcimator

Water Pipe Sizing Calculator

Size water supply piping based on fixture units, building height, available pressure, and pipe run length.

Inputs

FU

IPC Table 604.3: WC (tank) 2.2 FU; lavatory 1.0; shower 2.0; kitchen sink 1.4 per fixture

psi

IPC 604.1: minimum 15 psi at fixtures; IPC 604.5: maximum 80 psi (PRV required above 80)

ft

Results

Required Pipe Size

1 inches

Estimated Flow Rate12.9 GPM
Pipe Velocity5.27 fps
Friction Pressure Loss6.29 psi
How to Use This Calculator
  1. Enter total supply fixture units — use the Drainage Fixture Unit calculator to get this number.
  2. Enter the number of building floors and available pressure at the meter.
  3. Enter the longest pipe run in feet from meter to the most remote fixture.
  4. Review Required Pipe Size and Pipe Velocity — velocity should stay at or below 8 ft/s, the design maximum used to size the pipe.
  5. Check Friction Pressure Loss, calculated from the longest pipe run, to estimate how much of your available pressure remains at the fixture.

What each input means

Total Fixture Units
Total water supply fixture units (WSFU) for the building per IPC Table 604.3 or UPC Table A. Common values: water closet (tank) = 2.2 FU, lavatory = 1.0, bathtub = 1.4, kitchen sink = 1.4.
Number of Floors
Number of stories above the water entry point. Each floor adds elevation pressure loss.
Available Pressure
Static water pressure at the building entry point from the utility supply. IPC 604.1 requires minimum 15 psi residual at all fixtures; maximum 80 psi per IPC 604.5 (pressure reducing valve required above 80 psi).
Longest Pipe Run
Length of the longest pipe run from the water entry to the most remote fixture.

How this is calculated

Worked example, using the default values

  1. Identify Input Parameters
    4 parameters
    Total Fixture Units = 50, Number of Floors = 2, Available Pressure = 60, Longest Pipe Run = 100 = 4 input(s) provided
  2. Calculate Required Pipe Size
    Required Pipe Size
    1 = 1
  3. Calculate Estimated Flow Rate
    Estimated Flow Rate
    12.9 = 12.9
  4. Calculate Pipe Velocity
    Pipe Velocity
    5.27 = 5.27

Engine last updated . Checked against 1 independently-derived test — how we verify calculators.

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