Created By : Naaz Fatima

Reviewed By : Phani Ponnapalli

Last Updated : May 18, 2023

The properties of water flowing in a gravity-fed system can be calculated using the Free Pipe Flow Calculator. Simply enter the pipe diameter, material, pipe length, and drop details in the input fields to determine the flow speed and discharge. Lengthy calculations will be avoided with the help of this simple calculator.

Pipe diameter:
Pipe length:

What is Pipe Flow?

The pipe flow is a branch of fluid mechanics that deals with the flow of liquid in a closed container/pipe. The open channel flow is another type of liquid flow. The pipe flow, in general, has no open surface and is only confined to the closed conduit, thus it is not exposed to ambient pressure. Liquid flow via a pipe can be classed into two types: laminar flow and turbulent flow.

What is the Gravity Flow?

When the flow of water through a pipe is caused by gravity, it is known as gravity flow. As long as there is an altitude difference between the source water (upstream source) and the discharge point, the flow will occur. There must also be no external energy utilised to propel the water forward (such as via a pump).

The unique case of gravity flow, in which water flows via a closed pipe, is taken into account by our water flow calculator. Its speed is influenced not just by the slope and size of the pipe, but also by the material of the pipe. Because of its roughness, friction forms between the pipe's sides and the water, delaying the flow.

For more concepts check out to get quick answers by using this free tool.

Hazen-Williams Equation | Gravity Flow Definition

Gravity flow of water occurs when the flow of water in a pipe is caused by the gravitational force. The Hazen-Williams equation can be used to compute the water flow velocity.

The Hazen-Williams equation is only applicable for water. The formula is similar to this.v = k * C * R0.63 * S0.54

  • Where,
  • v = water flow velocity in the pipe (for the metric system is m/s, for the imperial system is ft/s)
  • C = roughness coefficient
  • R = hydraulic radius
  • S = slope of the energy line
  • k is the conversion factor (for the metric system, k=0.849, for the imperial system, k=1.318 f).

The roughness coefficient is determined by the pipe's material. The values for various pipes are listed below. The ratio of the pipe's area and perimeter is known as hydraulic radius.

Hydraulic radius R = A/P = πr²/2πr = r/2 = d/4

Divide the pipe length by the drop to get the slope of the energy line. The flow discharge Q is calculated using the following formula Q = AV

What is the Pipe Flow Calculator and How does it Work?

The Pipe Flow Calculator is a free online application that depicts the flow of liquid through a closed container. The online pipe flow calculator tool speeds up calculations and displays fluid flow in the pipe in a microsecond. The pipe flow calculator can be used in the following way

  • Step 1: In the unknown value input area, enter the velocity, pipe diameter, and x.
  • Step 2: To obtain the flow rate, click the "Calculate x" button.
  • Step 3: Last but not least, the output field will show the liquid flow in the pipe.

FAQs on Pipe Flow Calculator

1. Is the flow rate affected by pipe diameter?

Yes, because the flow rate is determined by the cross-sectional area of the pipe, it will grow as the pipe diameter squares. As a result, the flow rate decreases as the square of the pipe diameter increases.

2. How can you find out the volume flow rate in a pipe?

The speed of the liquid flowing through the pipe is multiplied by the cross-sectional area of the pipe.

3. What is a plastic pipe's roughness coefficient?

The roughness coefficient of a common plastic pipe is 150. The slower the gravity-fed flow through a pipe is, the higher the roughness coefficient.

4. What is the average flow rate?

At 32°F, the normal flow rate is 1 atmosphere (101.3 kPa) or 14.696 psi (0 0C). The volume of fluid that travels at a specific site at a given pressure and temperature is known as the real flow rate.

5. How much does a 4-inch sewer pipe fall?

The minimum slope is 1 inch in 8 feet, or 1/8-inch every foot, for 4-inch PVC piping and a building sewer less than 50 feet long, and the maximum slope is 1/4-inch per foot. The slope should be 1/4-inch per foot for sewers longer than 50 feet.