### i. Glossary

Term |
Description |
Units |

a | Acceleration | Metres/Second^{2} |

A | Area | Metres^{2} |

A_{t} |
Reservoir Supply Pipe Area | Metres^{2} |

D,d | Pipe Diameter | Metres/inches |

E | Energy | Joules |

E_{k} |
Kinetic Energy | Joules |

E_{p} |
Potential Energy | Joules |

F | Force | Newtons |

f | Friction Factor | – |

f_{A-n} |
Frictional Head Loss in Tap Supply Pipe | Metres |

f_{h} |
Frictional Head Loss | Metres |

f_{hl} |
Frictional Head Loss in Larger Diameter Pipe | Metres |

f_{hn} |
Frictional Head Loss in Pipe n | Metres |

f_{hs} |
Frictional Head Loss in Smaller Diameter Pipe | Metres |

f_{p} |
Frictional Loss (Pressure) | Newtons/Metre^{2} |

f_{t-A} |
Frictional Head Loss in Reservoir Supply Pipe | Metres |

g | Gravitational Acceleration | Metres/Second^{2} |

h | Height | Metres |

H | Desired Frictional Head Loss | Metres |

h_{A} |
Height of Junction A | Metres |

H_{A} |
Head at Point A | Metres |

h_{B} |
Height of Junction B | Metres |

H_{max} |
Maiximum Static Head | Metres |

h_{n} |
Height of nth Tap | Metres |

H_{n} |
Residual Head at Tap n | Metres |

h_{t} |
Reservoir Height | Metres |

I | Electrical Current | Amps |

L | Length | Metres |

L_{n} |
nth Tap Supply Pipe Length | Metres |

L_{t} |
Reservoir Supply Pipe Length | Metres |

M | Mass | Kilogrammes |

n | Number of Taps | – |

N_{RE} |
Reynolds Number | – |

P | Pressure | Newtons/Metre^{2} |

P_{A} |
Pressure at Junction A | Newtons/Metre^{2} |

P_{B} |
Pressure at Junction B | Newtons/Metre^{2} |

P_{k} |
Kinetic Energy as a Pressure | Newtons/Metre^{2} |

P_{n} |
Residual Pressure at nth tap | Newtons/Metre^{2} |

P_{p} |
Pump Pressure | Newtons/Metre^{2} |

P_{p} |
Potential Energy as a Pressure | Newtons/Metre^{2} |

P_{t} |
Turbine Pressure | Newtons/Metre^{2} |

Q,q | Volumetric Flow Rate | Metre^{3}/Second |

q_{A} |
Volumetric Flow Rate at Junction A | Metre^{3}/Second |

S | Distance | Metres |

t | Time | Seconds |

v | Velocity | Metres/second |

V | Volume | Metre^{3} |

V | Voltage | Volts |

v_{A} |
Velocity of Water in Reservoir Supply Pipe | Metres/Second |

v_{av} |
Average Velocity | Metres/Second |

v_{n} |
Velocity of Water in n^{th} Tap Supply Pipe |
Metres/Second |

W | Power | Watts |

W_{e} |
Electrical Power | Watts |

W_{in} |
Power Supplied to Pump | Watts |

W_{out} |
Power Supplied by Pump | Watts |

Δh | Total Difference in Head between Tanks | Metres |

ΔH | Residual Head | Metres |

ΔP | Residual Pressure | Newtons/Metre^{2} |

γ | Pump Efficiency | – |

μ | Kinematic Viscosity | Metres ^{2}/Second |

ρ | Density (ro) | Kilogrammes/Metre^{3} |

### ii. Scope

This manual is intended to aid the water projects worker or volunteer in the following ways :

- To explain, from first principals and using basic physical relations, the origin of the equations that design water systems.
- To systematically outline the key equations and explain how to apply them to scenarios where there is no text book method readily available.
- To give step by step numerical solutions to some of the more common and also some special scenarios.
- To systematically lay down the design parameters for gravity flow water systems and show how they should be applied to a design.

Sections 2-7 explain the basic concepts, show how the core equations are derived, explain perfect and imperfect systems and cover the analysis of pumps and turbines.

Sections 8 and 9 show how to apply the core equations to a series of common and special scenarios.

The worked examples 1-8 show how to simplify the equations developed in Sections 8 and 9 for practical use and give step by step numerical examples for each scenario. In addition worked example 9 shows the design process applied to a sample gravity flow water system design.

Appendices 1-6 give more complex derivations of the core relations, explanations of useful processes in the calculations and additional technical data.

For the experienced water system designer I would suggest reading through Sections 8 and 9, Appendix 4 and Worked Example 9 in particular.

Any questions about this manual should be addressed to Dodger at dodger@irational.org.

### iii. References

*A Handbook of Gravity-Flow Water Systems*: Thomas D.Jordan Jnr. : Intermediate Technology Publications 1996.*Basic Engineering Sciences and Structural Engineering for Engineer-in-Training Examinations*: Apfelbaum & Ottesen : Hayden Book Company 1970.*Friction Loss Characteristics Chart*:*Polyethylene (PE) SDR-Pressure Rated Tube*: PISTA & Gustavo Urbano.

### iv. Notes

- In the numerical calculations for the Worked Examples, the asterisk (*) denotes the multiplication sign and the slash (/) the divide sign.
- In general, metric fundamental units (Metres, Kilogrammes and Seconds) have been used in the Worked Examples, the two main exceptions being inches for pipe diameters and Litres/Second (LPS) for flow rates.