25/06/2013

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Rainwater Tank Workshop

Why harvest rainwater?

• To replace mains water use

• Increase environmental river flows

• Resilience and diversity

• Less desalinated water

• Drought proofing

• Reduce stormwater runoff

• Improve water quality

What to use rainwater for?

• Watering gardens

• Topping up pools

• Car washing

• Toilet flushing

• Clothes washing

• Showering and bathing

• Drinking?

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How do we use water in the home

Clothes washer, 45, 22%

Shower/Bath, 55, 27%

Tap , 25, 13%

Dishwasher, 5, 3%

Toilet, 30, 15%

Garden, 40, 20%

Some interesting statistics

Ipart (2003)

Connect more uses because:

• The more uses you supply

• The faster the tank empties

• Leaving more space in the tank

• To collect rainwater next time it rains

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Harvesting

Amount of rainwater captured depends on:

• Collection area (roof)

• Tank size

• Rainwater usage

Roof runoff quality

What’s in my rainwater?

• Relatively clean compared to other sources (greywayer, wastewater, stormwater) but…

• Rainwater contains heavy metals

– Lead flashing!!

– Galvanised metal roofs (Zinc, Aluminium)

– For roofs with no metal sources generally below drinking water guidelines safe levels

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• Study on 80 rainwater tanks in 34 suburbs (Toze, 2012)

What’s in my rainwater?

What’s in my rainwater?

• Rainwater contains pathogens

– Many tests have shown pathogens in rainwater again and again

– Have to assume pathogens in rainwater tank

• Epidemiological study in Adelaide (Heyworth, 2006)

• NSW Health does not recommend rainwater tanks for drinking in areas where a potable mains water supply is available (e.g. most of Sydney).

What’s in my rainwater

• Sediment, organics

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What’s in my rainwater

• Mosquitoes

• Use screened inlets and outlets

Roof runoff

Maximise roof collection area

• Rainfall x Area = roof runoff

• For example a 5mm rainfall event on a 100 sqm roof

– 5 x 100 = 500L (or 0.5 kilolitre)

• For example a 10mm rainfall event on a 50 sqm roof

– 10 x 50 = 500 L (or 0.5 kL)

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Assess roof area

• Area draining to back roof 115 m2

Calculate Roof Area

Where are the downpipes?

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Where are the downpipes?

Determining Usage

Determine what to plumb it into?

• Where are things in the house?

LH

B

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Where to plumb to?

BL H

Determine Usage

• Per person in a water efficient household

Usage per person Litres/Day

Toilet 20

Kitchen 10

Clothes Washer 15

Hand basin 5

Bath/Shower 50

Total 100

Usage – Garden Calculating Seasonal USe

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Usage – Garden Calculating Seasonal USe

• Garden usage calculations:

• 10 litres per watering can

• 20 litres per minute hosing

• Watering frequency:

– Gardens once or twice a week

– Lawns every second day in summer

Calculating your water use

• Toilet flushes:– 6/3 L dual flush – 20 L/p/d

– 9/5 L dual flush – 40 L/p/d

– 12 L Single flush – 60 L/p/d

• Showers/bath– (AAA) 9 L/min x 5 mins = 45 L

– Old shower 15 L/min x 5mins = 75 L

– Bath (half full) = 100 L

• Clothes Washer– Front loader – 60 to 80 L

– Top loading machine 100 to 150 L

Calculating tank size

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Calculating tank size

• http://tankulator.ata.org.au/

Tankulator

Tankulator

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Questions to ask tankulator

1. How much water do I save if I plumb it into different areas of the house

For example 5 kL tank plumbed to:

– Garden only: 21.9 kL/yr

– Garden & Toilet : 38.3 kl/yr

– Garden, Tlt &Laundry: 61.4 kl/yr

– Garden, Tlt, L and hot water: 75.8 kl/yr

Questions to ask tankulator

1. How much water do I save if I plumb it into different areas of the house

For example 5 kL tank plumbed to:

– Garden only: 21.9 kL/yr

– Garden & Toilet : 38.3 kl/yr

– Garden, Tlt &Laundry: 61.4 kl/yr

– Garden, Tlt, L and hot water: 75.8 kl/yr

0

10

20

30

40

50

60

70

80

G G+T G+T+L G+T+L+H

Wat

er S

aved

kl/

yr

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Questions to ask tankulator

2. How big should my tank be?

For example plumbed to Gardens, toilet and laundry

– 0.5 kL tank: 31.0 kl/yr

– 1 kL tank: 39.6 kL/yr

– 2 kL tank: 50.9 kl/yr

– 5kL tank: 61.4 kl/yr

– 10 kl tank: 62.4 kl/yr

Questions to ask tankulator

2. How big should my tank be?

For example plumbed to Gardens, toilet and laundry

– 0.5 kL tank: 31.0 kl/yr

– 1 kL tank: 39.6 kL/yr

– 2 kL tank: 50.9 kl/yr

– 5kL tank: 61.4 kl/yr

– 10 kl tank: 62.4 kl/yr

0

10

20

30

40

50

60

70

0 2 4 6 8 10 12

Tank Size (kL)

Wat

er S

aved

(kL

/yr)

Questions to ask tankulator

3. How much roof do I need to capture?

For example 5 kL tank plumbed to Gardens, toilet and laundry

– 25 sqm 25.2 kl/yr

– 50 sqm: 42.4 kl/yr

– 100 sqm: 61.4kl/yr

– 150 sqm: 62.4 kl/yr

– 200 sqm: 62.4 kl/yr

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Questions to ask tankulator

3. How much roof do I need to capture?

For example 5 kL tank plumbed to Gardens, toilet and laundry

– 25 sqm 25.2 kl/yr

– 50 sqm: 42.4 kl/yr

– 100 sqm: 61.4kl/yr

– 150 sqm: 62.4 kl/yr

– 200 sqm: 62.4 kl/yr

0

10

20

30

40

50

60

70

0 50 100 150 200 250

Tank Size (kL)

Wat

er S

aved

(kL

/yr)

BREAK

Tank Types

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Round Tanks

• Steel or plastic

• Large range of shapes

• Best value

3000L plastic $800

3000L steel $1,300

10,000L plastic $1,800

Slim Line Tanks

Slimline tanks

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Slim Line Tanks

• Up to about 5,000L

• Steel or plastic

• More expensive than round tanks

• 3,000 L plastic $1,200

• 3,000 L steel $2,000

Under house

• Easier to collect from all downpipes of house

• Need about 0.7m clearance

• Mains bypass more difficult

• Harder to control water quality (e.g. first flush)

• More complicated install

• 3,000 L for $1,200

Bladder tank

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In-ground tanks

In-ground tanks

In-ground tanks

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In-ground tanks

• Concrete or plastic

• Doesn’t take up yard

• Easy to collect from whole house

• Higher risk of contamination (from stormwater runoff over ground)

• Testable backflow prevention required with annual testing

• Higher cost due to excavation required

• Not recommended in shallow bedrock areas (very expensive in rock)

Against wall

Rainwater hog

220m wide

Collection Systems

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Gutter guards

Leaf shedding inlets

First Flush Diverter

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Supply

• Gravity feed to garden

• Supply pressure pump

• Big difference in pumps

– Recommended brands

(Davey/Grundfos)

• Consider noise

• Pump housing

• Submersible

Look at Pump Curves

Automatic switching devices

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Maintenance

• Keep gutters clean (varies depending on roof)

• Maintain inlet and outlet screens (every 3 months)

• Clean out first flush diverter (monthly)

• De-sludge tank (every 5 to 10 years)

Regulations

Regulations

• Complies with SEPP 2008 (exempt development code)?

– Less than 10 kL in size

– Less than 450mm from boundary

– Located behind front building alignment

– Less than 2.4m in height

– Collects roof water only

– No offensive noise from pumps

• Yes: No DA required

• No: DA must be lodged with Council

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Regulations

• Plumbing must be in accordance with standards AS3500

• Connection to mains must be carried out by a notified plumber and licenced electrician for pump

• Fair Trade/Sydney Water must be notified of interconnection with mains (plumber will do this)

• Fair Trade will inspect installation including connection to mains water

Final Questions?