Pipe volume is an important calculation that is commonly used by various members of a project team during the design of a construction project.
Some examples of where the pipe volume calculation and results are used are:
The structural engineer will design their structure to handle the weight of pipes
The plumbing engineer needs to be aware that long 'dead-legs' have lots of consequences. 'Dead-legs' are the cold water that is drawn off before heated water commences to discharge from the heated water outlet e.g. waiting for the cold water to turn warm before getting into the shower. The consequences of having long dead-legs are:
The end-user will be unhappy waiting a long time for warm water, especially if they are in a building such as a luxury hotel
The client will not want to cover expensive bills from the wasted water and energy
Sustainability consultants often like to minimise the wasted water and energy to achieve a better rating for building's sustainability
Pipe Volume Formula
It is relatively easy to calculate the volume of water in a pipe by yourself, using a simple formula.
The volume of water in a pipe is calculated by multiplying the internal diameter of the pipe by its length. The calculation is dependent on two factors:
1. The internal diameter or the radius of a pipe
(as the diameter or the radius of a pipe increases, the pipe volume also increases)
2. The length of the pipe
(as the length of a pipe increases, the pipe volume also increases)
The volume of a pipe is measured in litres (L), metres cubed (m³), or gallons (gal).
The formula that you can use to measure the volume of a pipe is:
V = π⋅(D/2)²⋅L
In the pipe volume formula:
V is the pipe volume
D is the diameter of the pipe
L is the length of the pipe
π has a constant value of 22/7 (3.14)
Wait Time Formula
Once you know the pipe volume, you can also calculate how long you will need to wait for the water to come out of the outlet (e.g. the shower or sink).
The outlet flow rate is measured in litres per second (L/sec), metres cubed per second (m³/sec), or gallons per minute (gpm).
The formula that you can use to measure the wait time is:
T = V / Q
In the wait time formula:
T is the time
V is the pipe volume
Q is the outlet flow rate
Free Pipe Volume & Wait Time Spreadsheet
How to Use The Pipe Volume and Wait Time Spreadsheet
The pipe volume calculator comes with simple instructions. As shown below, you are required to enter information into certain cells and the results will be provided:
If you want to calculate the volume across multiple sections of pipes that differ in size, the pipe volume spreadsheet is set up to allow you to get those results too.
It is very important that you use the internal pipe diameter in the calculation, using the nominal or outside pipe diameter will produce the wrong results.
The spreadsheet also includes some generic pipe data but please do some research to ensure they are correct for your application before using them.
Create a Pipe Volume Chart
You can also create your own charts in the pipe volume spreadsheet.
Again, there are simple instructions that direct you to enter information into certain cells and the results will be provided:
Once you have created the chart, you can export it as a PDF to be referred to in the future.
How Can H2X Help With Pipe Volume Calculations?
When you use H2X, the pipe volume calculation is automatically undertaken as you draw your layout. The results are shown below:
You can also export a PDF of the project with the dead-leg results showing. You can share this with the project team to provide evidence that the plumbing system has been designed with the pipe volume and dead-legs in mind.
Want to Learn More About Pipe Volumes and Dead Legs?
You can read this post about why 'length' should not be used as a measurement for dead-leg calculations.