California Pipe Flow Metering Method
Calculate the discharge length from the open end of a partially filled horizontal pipe.
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.
The discharge can be calculated as
q = 8.69 (1  a / d)^{1.88} d^{2.48} (1)
where
q = discharge (ft^{3}/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 ft^{3}/s = 0.0283168 m^{3}/s = 101.9 m^{3}/h = 28.32 dm^{3}(litre)/s = 60 ft^{3}/min = 373.7 Imp.gal (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 ft^{3}/s
California Pipe Flow Calculator  Imperial Units
California Pipe Flow Calculator  Metric Units
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