Index

Instructions for using the utility to calculate pipe size according to flow rate

One of the most renowned methods of pipe sizing is using the Hazen-Williams equation, especially when the fluid involved is water.

The equation estimates the frictional loss (feet) for a specific pipe with Length, L (feet), Diameter, D (inch), Flowrate, Q (usgpm) and C-value: Hazen-Williams coefficient, C.

The C-value of different materials of pipes can be referenced from various sources, which are summarized below. The higher the C-value, the “smoother” the flow in the pipe.

TYPE OF PIPE/LOẠI ỐNG	C VALUE/ GIÁ TRỊ C
General Metal (Extremely smooth) - Ống kim loại tổng hợp cực nhẵn	130
Cast Iron (CI) - Ống Gang	100
Cast Iron Cement Lined (CICL) - Ống gang lót xi măng	130
Cast Iron Bituminous Lined (CIBL) - Ống gang lót Bitum	130
Cast Iron (Asphalt Coated) - Ống gang (phủ nhựa đường)	100
Ductile Iron (DI) - ống gang dẻo	110
Ductile Iron Cement Lined (DICL) - Ống gang dẻo lót xi măng	130
Mild Steel (MS) - Ống thép nhẹ	120
Mild Steel Cement Lined (MSCL) - Ống thép nhẹ lót xi măng	130
Galvanised Iron (GI) - Ống sắt mạ kẽm	120
Stainless steel - Ống inox	140
Steel - Ống thép	100
Steel (Corrugated) - Ống thép tole	60
Copper (Cu) - Ống đồng	140
Aluminium (Al) - Ống nhôm	130
Brass (Br) - Ống thau	130
Lead - Ống chì	130
Tin - Ống thiếc	130
Corrugated metal - Ống kim loại tole quấn	60
Reinforced glass fibre (FRP) - Ống composite	140
Plastic (General) - Ống nhựa tổng hợp	130
High-density polyethylene (HDPE) - Ống HDPE	150
Acrylonite Butadiene Styrene (ABS) - Ống nhựa ABS	130
Polyethylene (PE) - Ống nhựa PE	140
Polyvinyl chloride (PVC, CPVC) - Ống nhựa PVC, CPVC	150
Spun Cement - Ống xi măng ly tâm	130
Concrete - Ống bê tông	100
Vitrified clay - Ống đất sét thuỷ tinh	110
Wooden - Ống gỗ	110
Masonry - Ống xây dựng	110
Glass - Ống thủy tinh	130

We can use the Hazen-Williams equation to estimate pipe sizes D, required for a given pipe C-value, flowrate Q, and the allowable frictional loss over a fixed 100 feet length of pipe (30m). This “ft/100ft or m/30m” maximum allowable friction loss is commonly set in the range within 4 to 10ft/100ft (1.2 to 3m). 4ft/100ft means that 4 feet of loss is the maximum that can be accepted in our design per 100 feet run of pipe. This value is then referred in a pipe size chart as shown below.

Instructions for using the pipe size calculation utility with images

Utility interface:

Water Pipe Size Calculator

		Unit
Types of Pipe
C-Value of Pipe (Hazen-Williams coefficient)
Flowrate		M3/H
Maximum Allowable Frictional Loss From 1,2 to 3,0. The smaller the pipe diameter, the higher this loss, value 1.2 is the average allowable value.		m/30m dài
Min. Required Pipe Internal Diameter		mm
Selected pipe size DN		mm
Selected pipe size inch		Inch
Water velocity in the pipe		m/s
Flowrate		usgpm
Maximum Allowable Frictional Loss		ft/100ft
Min. Required Pipe Internal Diameter		Inch
% tolerance to the imposed allowable friction loss*		%

Input data

Step 1: Select the frame: Select the types of pipe, you need to choose the correct pipe material you are using to be able to access the corresponding C value. For example, choose stainless steel pipes

Step 2: Enter the water flow rate through the pipe, the unit is m3/h. For example, enter 20m3/h

Step 3: The maximum allowable friction loss frame, according to the above analysis, can be chosen in the range of 1,2-3,0. For example, choose 1,2

Result:

Step 4: Minimum required internal diameter to meet the flow rate with the selected loss. It is 67,05mm

Step 5: Suggest pipe diameter according to DN (mm). This recommendation for rounding up to even size is based on commonly available pipe sizes on the market. It is 80mm

Step 6: Suggest pipe diameter in Inches. This recommendation for rounding up to even size is based on commonly available pipe sizes on the market. It is 3inch

Step 7: Velocity of water flowing in the pipe in m/s, this value is appropriate in the range of 0,9-2,4. It is 1,1

Then the result will be as follows:

If you have questions about how to calculate pipe size, please contact our Company’s Sales department for more detailed instructions.

Instructions for using the utility to calculate pipe size according to flow rate