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California Pipe Flow Metering Method

Calculate the discharge length from the open end of a partially filled horizontal pipe.

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With the California Pipe Flow Metering Method the discharge from the open end of partially filled horizontal pipes discharging freely into the air can be measured.

Califorina Pipe Flow Metering Method

The discharge can be calculated as

q = 8.69 (1 - a / d)1.88 d2.48                           (1)


q = discharge (ft3/s)

a = distance in the plane end of the pipe - from the top of the inside surface of the pipe - to the water surface (ft)

d = internal diameter of pipe (ft)

The equation is empirical and can be used for pipes in the diameter range 3 - 10 in

  • 1 mm = 0.00328 feet
  • 1 ft = 0.3048 m = 12 in = 0.3333 yd = 30.48 cm = 304.8 mm
  • 1 ft3/s = 0.0283168 m3/s = 101.9 m3/h = 28.32 dm3(litre)/s = 60 ft3/min = 373.7 (UK)/min = 448.9 gal (US)/min (US gpm)

California Pipe Flow Example

In the discharge on a horizontal 4 inches PVC sewer pipe the distance from the top inside pipe to the water flow is 3 inches (0.25 ft). The inside diameter of the PVC pipe is 4.069 in (0.34 ft)

The discharge can be calculated as

q = 8.69 (1 - (0.25 ft) / (0.34 ft))1.88 (0.34 ft)2.48      

   = 0.049 ft3/s

California Pipe Flow Calculator - Imperial Units

d - inside diameter of pipe (ft)

a - distance between top inside pipe to water surface (ft)

California Pipe Flow Calculator - Metric Units

d - inside diameter of pipe (mm)

a - distance between top inside pipe to water surface (mm)

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Related Topics

Flow Measurement

Flow metering principles - Orifice, Venturi, Flow Nozzles, Pitot Tubes, Target, Variable Area, Positive Displacement, Turbine, Vortex, Electromagnetic, Ultrasonic Doppler, Ultrasonic Time-of-travel, Mass Coriolis, Mass Thermal, Weir V-notch, Flume Parshall and Sluice Gate flow meters and more.

Sanitary Drainage Systems

The purpose of the sanitary drainage system is to remove effluent discharged from plumbing fixtures and other equipment.

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