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# Equivalent Length Method - Minor Pressure Loss in Piping Systems

## Calculate minor pressure loss in piping systems with the Equivalent Pipe Length Method.

An efficient and simple way to calculate the pressure loss in a piping system is the "Equivalent Pipe Length Method".

### 1. Make a Diagram of the Piping System

Make a diagram where the system is structured with nodes as shown below.

In the very simply circulating system used in this example the first node (0) is the pump. The next node is the tees (2) where the piping system splits up. The other nodes are the heating radiators.

In many systems the structure can be simplified as above since the piping in both directions are of same size. If a more fine grained approach is required, additional nodes can be added in both directions as shown below.

### 2. Make a calculation table

With the most simplified nodes structure above a calculation table can be made as shown below. Each section from node to node is calculated by supplying length, volume flow, pipe size, pressure loss from diagrams or tables for the actual pipes and components in the sections and their individual equivalent length substituting the the minor loss.

Note! The flow and pressure units must be adjusted to the data available for your piping system.

### 3. Add Volume flow, Pipe Size and Pressure Loss for each Section

Add actual pipe size and in each section. Use tabulated data or a diagrams.

The pressure loss may alternatively be calculated with the Hazen-Williams Equation or the Darcy-Weisbach Formula.

• Pressure loss for many types of pipes can be found here.

### 4. Add Equivalent Length of all Valves, Fittings and Straight Pipes

Add the equivalent length of all valves, components, fittings and straight pipes in the sections.

### 5. Summarize the Pressure Loss in each Section

Calculate and summarize the pressure loss in each section.

### 6. Summarize the Pressure Loss in all Paths

Finally, add up the pressure loss in all sections that form unique paths. In the example above there are two unique paths - one is section 0 - 2 - 3, the other is section 0 - 2 - 4. Add extra columns for additional paths in more complicated systems.

The highest pressure loss determines the pump head.

Add valves where it is necessary to balance the system. In the example above a balancing valve is added in section 2-4.

Note! The Equivalent Pipe Length Method can be adapted to most piping systems - like water supply systems, gravity heating systems and similar.

## Related Topics

• Heating - Heating systems - capacity and design of boilers, pipelines, heat exchangers, expansion systems and more.
• Design Strategies - Piping systems design strategies - documentation, P&ID, flow diagrams - capacities and limits.
• Fluid Flow and Pressure Loss - Pipe lines - fluid flow and pressure loss - water, sewer, steel pipes, pvc pipes, copper tubes and more.

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Temperature

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oF

Length

m
km
in
ft
yards
miles
naut miles

Area

m2
km2
in2
ft2
miles2
acres

Volume

m3
liters
in3
ft3
us gal

Weight

kgf
N
lbf

Velocity

m/s
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ft/s
mph
knots

Pressure

Pa (N/m2)
bar
mm H2O
kg/cm2
psi
inches H2O

Flow

m3/s
m3/h
US gpm
cfm

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