The roughness coefficient CCC depends on the material of the pipe. You can pick a material from the drop-down list of our tool or select the last option to manually input the value of CCC if you know the roughness coefficient of your flow system. We use the following values:

Gasvelocityinpipe Calculator

The Hazen-Williams equation is an empirically derived formula that describes the velocity of water in a gravity flow. Remember that the Hazen-Williams equation is valid only for water – applying it for any other fluid will give you inaccurate results. It also doesn't take into account the temperature of the water, and is only accurate for the 40-75 °F (4-25 °C) range.

Let's use the pipe flow calculator to determine the velocity and discharge of a plastic pipe, 0.5 feet in diameter. The pipe is 12 feet long, and the difference in height between the beginning and endpoints of the pipe is equal to 3 feet.

Pipe velocity

To calculate the slope SSS, you must divide the drop (height difference between the beginning and endpoints) by the pipe length. Remember that if the pipe slope is not constant but changes all the time, the actual water flow speed will differ from the obtained result.

Calculatevelocityinpipefrom pressure

The gravity flow of water is when the flow of water in a pipe is caused by the force of gravity. The flow will happen as long as there is an altitude difference between the source water (upstream source) and the discharge point. There must also be no external energy (for example, from a pump) used to move the water forward.

That's it! You just found the speed and discharge of a gravity flow. Have you already seen the pipe volume calculator? That's another tool that considers the liquids flowing through pipes.

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Pipe velocity Calculatormetric

First use the Hazen-Williams equation to find the velocity of the fluid: v = k × C × R0.63 × S0.54. In this equation, k is either 0.849 for metric or 1.318 if using imperial units, C is the roughness coefficient of the pipe material, R is the hydraulic radius (cross-sectional area divided by perimeter), and S is the slope of the pipe.

Gravitypipeflowcalculator

For a typical plastic pipe, its roughness coefficient is 150. The higher the roughness coefficient, the faster the gravity-fed flow through a pipe will be.

Use this pipe flow calculator to analyze the properties of water flowing in a gravity-fed system. You only need to know the diameter of the pipe, the material it's made of, its length, and the drop in height. We then apply the Hazen-Williams equation for you, which calculates the resulting velocity and discharge. Interested? Read on to discover the formulas we use and to see an easy-to-follow example calculation.

You can then calculate the volume that flows through the pipe per second by multiplying v by the cross-sectional area of the pipe.

Pipeflowvelocity

Pipe VelocityChart

Our water flow calculator takes into consideration the particular case of gravity flow, where the water flows in a closed pipe. Its velocity is influenced not only by the inclination and size of the pipe but also by the pipe material. Its roughness causes friction between the sides of the pipe and the water, decreasing the water speed. Also, in the coefficient of discharge calculator, we described the metric related to the theoretical and actual flow rates. Be sure to check it out if you're interested!

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Yes, this is because the flow rate is directly related to the pipe's cross-sectional area. When the cross-sectional area increases (which happens when the pipe diameter increases), the flow rate increases, too. Similarly, as the diameter decreases, the flow rate decreases.

Sewerpipe velocity Calculator

The hydraulic radius, RRR, is the proportion between the area and the perimeter of your pipe. If the pipe is circular, you will find it according to the following equation:

Once you know the velocity of the gravity flow, you can also find the discharge, QQQ, by multiplying the cross-sectional area of the pipe by the flow speed:

where rrr is the pipe radius, and ddd is the pipe diameter. By ticking this pipe flow calculator's Display more calculated variables checkbox, you can view and modify all these parameters (area, perimeter, hydraulic radius).

Make sure to use our flow rate calculator to convert between the discharge (volumetric flow rate) and the mass flow rate.

You don't need to know the values of CCC, RRR, or SSS in order to use our pipe flow calculator – we calculate them for you!