rainwater harvesting in oatley jim vickery oatley flora and fauna society monday 27 th october 2014
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Rainwater Harvesting in Oatley
Jim Vickery
Oatley Flora and Fauna SocietyMonday 27th October 2014
Introduction
Rainwater harvesting questions:• How much water will I need each day?•Where can the rainwater tank be installed
to maximise the area of the roof used to collect rainwater?• How much rain is going to fall onto the
roof?•Will the rain come in showers or storms?• Best size for the rainwater storage tank?
Typical domestic water usage: L/dayNo. of people 2 4 6
Economical toilet 36 72 108
Economical toilet & economical clothes washing machine
236 422 558
PLUS – water for the garden
Oatley NSW rainfall characteristics:• Drier than many Sydney suburbs• Misses out on the coastal rainfall that
only comes as far as King Georges Rd. • Rain from the west tends to go to the
north and to the south!
0 10 20 30 40 50 60 70 80 90 1000
20
40
60
80
100
120
IDEALDRYBIG EVENT
DAYS
TANK CONTENTS
%
Tank storage perform-ance
A reliable supply
QuarterAverage(1993 to
2013)1996 2004
Q1 280 mm
Q2 265 mm
Q3 184 mm
Q4 200 mm
Annual 929 mm
Estimate of the reliable draw based on:• 1996 – an average year for rainfall • 2004 – a very dry winter
QuarterAverage(1993 to
2013)1996 2004
Q1 280 mm 277 222
Q2 265 mm 295 76
Q3 184 mm 272 184
Q4 200 mm 134 337
Annual 929 mm 978 819
Estimate of the reliable draw based on:• 1996 – an average year for rainfall • 2004 – a very dry winter
Usage: L/day 100Roof area: sq m 100
Storage: L 2000 4000 6000 8000Minimum water stored during the quarter
1996Average summer
1996Average winter
2004Dry winter
Days pa without water19962004
Usage: L/day 100Roof area: sq m 100
Storage: L 2000 4000 6000 8000Minimum water stored during the quarter
1996Average summer 5% 52% 68% 75%
1996Average winter 0% 20% 47% 60%
2004Dry winter 0% 0% 0% 9%
Days pa without water1996 25 0 0 02004 57 36 15 0
0 20 40 60 80 100 120 140 160 180 2000
50
100
150
200
250
300
Avg Sum 6000L
Avg Sum 2000L
Roof Area (sq m)
Relia
ble
Dra
w (L
/d)
0 20 40 60 80 100 120 140 160 180 2000
50
100
150
200
250
300Avg Sum 6000L
Avg Win 6000L
Dry Win 6000L
Roof Area (sq m)
Relia
ble
Dra
w (L
/d)
0 20 40 60 80 100 120 140 160 180 2000
50
100
150
200
250
300 Avg Sum 6000L
Avg Sum 2000L
Avg Win 2000L
Dry Win 2000L
Roof Area (sq m)
Relia
ble
Dra
w (L
/d)
Collection equipment
Best value
Style Material Indicative cost - $/kL (2,000 to 5,000L)
1 Round Poly $220
2 Round Steel $320
3 Slimline Poly $400
4 Underdeck Poly $550
5 Slimline Steel $600
6 Underground
Poly $700 plus excavation
Rainwater tank types and costs
OVERFLOWFIRST FLUSH
FINE SCREEN
20 mm dia40 mm dia50 mm dia
FLAP
External self priming pump with controller mounted above the motor.
Submersible pump with external controller – changeover unit
Surface water
Banksia Robur
Conclusion
Rainwater tank installation guidelines:1. Determine your daily need for rainwater.2. Determine the size of your available roof
catchment area.3. A 2000 L tank will provide 50 to 100 L/day from
a 100 sq m or larger roof.4. A 6000 L tank or larger is necessary for
supplying a washing machine or something similar. If the roof catchment area is greater than 200 sq m then the tank is less likely to empty out during dry periods .
0 20 40 60 80 100 120 140 160 180 2000
50
100
150
200
250
300Avg Sum 6000LAvg Win 6000LDry Win 6000LAvg Sum 2000LAvg Win 2000LDry Win 2000LRoof Area (sq m)
Relia
ble
Dra
w (L
/d)
Oatley Flora and Fauna Society27th October 2014
Rainwater Harvesting in OatleyJim Vickery
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