Preface

i. Glossary

Term	Description	Units
a	Acceleration	Metres/Second2
A	Area	Metres2
At	Reservoir Supply Pipe Area	Metres2
D,d	Pipe Diameter	Metres/inches
E	Energy	Joules
Ek	Kinetic Energy	Joules
Ep	Potential Energy	Joules
F	Force	Newtons
f	Friction Factor	–
fA-n	Frictional Head Loss in Tap Supply Pipe	Metres
fh	Frictional Head Loss	Metres
fhl	Frictional Head Loss in Larger Diameter Pipe	Metres
fhn	Frictional Head Loss in Pipe n	Metres
fhs	Frictional Head Loss in Smaller Diameter Pipe	Metres
fp	Frictional Loss (Pressure)	Newtons/Metre2
ft-A	Frictional Head Loss in Reservoir Supply Pipe	Metres
g	Gravitational Acceleration	Metres/Second2
h	Height	Metres
H	Desired Frictional Head Loss	Metres
hA	Height of Junction A	Metres
HA	Head at Point A	Metres
hB	Height of Junction B	Metres
Hmax	Maiximum Static Head	Metres
hn	Height of nth Tap	Metres
Hn	Residual Head at Tap n	Metres
ht	Reservoir Height	Metres
I	Electrical Current	Amps
L	Length	Metres
Ln	nth Tap Supply Pipe Length	Metres
Lt	Reservoir Supply Pipe Length	Metres
M	Mass	Kilogrammes
n	Number of Taps	–
NRE	Reynolds Number	–
P	Pressure	Newtons/Metre2
PA	Pressure at Junction A	Newtons/Metre2
PB	Pressure at Junction B	Newtons/Metre2
Pk	Kinetic Energy as a Pressure	Newtons/Metre2
Pn	Residual Pressure at nth tap	Newtons/Metre2
Pp	Pump Pressure	Newtons/Metre2
Pp	Potential Energy as a Pressure	Newtons/Metre2
Pt	Turbine Pressure	Newtons/Metre2
Q,q	Volumetric Flow Rate	Metre3/Second
qA	Volumetric Flow Rate at Junction A	Metre3/Second
S	Distance	Metres
t	Time	Seconds
v	Velocity	Metres/second
V	Volume	Metre3
V	Voltage	Volts
vA	Velocity of Water in Reservoir Supply Pipe	Metres/Second
vav	Average Velocity	Metres/Second
vn	Velocity of Water in nth Tap Supply Pipe	Metres/Second
W	Power	Watts
We	Electrical Power	Watts
Win	Power Supplied to Pump	Watts
Wout	Power Supplied by Pump	Watts
Δh	Total Difference in Head between Tanks	Metres
ΔH	Residual Head	Metres
ΔP	Residual Pressure	Newtons/Metre2
γ	Pump Efficiency	–
μ	Kinematic Viscosity	Metres 2/Second
ρ	Density (ro)	Kilogrammes/Metre3

ii. Scope

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

1. To explain, from first principals and using basic physical relations, the origin of the equations that design water systems.
2. To systematically outline the key equations and explain how to apply them to scenarios where there is no text book method readily available.
3. To give step by step numerical solutions to some of the more common and also some special scenarios.
4. 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

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

iv. Notes

1. In the numerical calculations for the Worked Examples, the asterisk (*) denotes the multiplication sign and the slash (/) the divide sign.
2. 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.