# 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

*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)*