Sustainable Solutions April 2009

SUPPLY CHAIN
and price a suitable system. It is easier to the tank maintains pressure to the toilets and
install a system during a new build or a major washing machine, turning off automatically
INSTALLING A RAIN-
renovation project, but it is certainly possible to when not needed.
WATER HARVESTER
retroﬁ t.” Bicknell says: “State-of-the-art ﬁ lters
In addition to the cost of the materials, the are a great beneﬁ t; they are self cleaning so
most costly of the installation costs are digging maintenance is reduced to am minimum.
the hole for the underground storage tank (to "Just take a look every year or so to make
be recommended to keep rainwater fresh) and sure the ﬁ lter is nice and clear”.
ﬁ tting a separate supply network to WCs and According to Grave: “Most systems are in
the washing machine. kit format which can be installed by the home
owner. In terms of work, the installation is
‘
The cost of
similar to that of a sewage treatment system.
You’d need a machine to shift around three
an average kit
tonnes of soil and a plumber involved in some
stages of the installation.”
Step 1
with a 3750
In the garden Work out the size of tank you require, this
For many keen gardeners and vegetable
will depend on your geographical area,
Water, water
litre tank is
growers, rain harvesters make even more sense.
roof size and usage. It is not difficult to
Grave, who has her own rain harvester
work out your requirements. You can
get a tank size calculator online. www.
£2,500
The cost of an average kit with a 3
’
which she estimates saves her up to £200 a
rainwaterharvesting.co.uk/calculator.php
year in water bills, points out: “There’s a real
worry for gardeners when plants and lawns are Step 2
750 litre threatened by a ban on watering that would
Rainwater is captured from
tank and all accessories is £2,500. cause destruction of years of investment. Using
the roof and brought to a
In a retroﬁ t, installation could well be available rain water from house and green
central point, via normal
another £1,000, but the cost would be much less house roofs to be then channelled into a tank
guttering and down-pipes,
and filtered on entry
if builders and plumbers were already on site. can provide a real measure to allow continued
to a storage tank
So how does the science work? watering of plants.”
(underground,
Bicknell explains: “First, plug into the tank size Many systems can be used as the water store
where the
calculator the size of the roof. A small house for irrigation systems, or as a second supply
water stays
(90m
2
roof) in the home counties (78cm of rain tank for an existing system. crystal clear).
a year) will gather 55,000 litres a year (we say Some gardeners link the tanks with a pump
A submersible
20% of the water goes to waste with leaves and to supply water via a stand-pipe system or into
pump delivers the
debris).” a greenhouse with an automated year round
water to toilets and
This amount equates to 150 litres a day, drip pipe irrigation supply, adds Grave.
washing machines and
for outdoor use on demand.
enough for washing machine and toilets for
three people, he adds.
Grants and legislation
Step 3
A smallish underground tank of 3750 litres Currently no grants exist to encourage private
Choose a suitable mains backup facility,
would continue providing water for two weeks householders to collect and use rainwater.
which is necessary particularly if using
if there were no rain shower. But most family However, the trend is said to be moving
rainwater in the home to feed appliances.
houses (150-250 m
2
roof) get 200,000 litres a that way.
The cheapest option is a solenoid valve,
which simply puts some mains water
year; in this case a 6500 litre tank gives enough Grave says: “Businesses can already recoup
into the rainwater tank when empty.
for both the house and the garden. 100% of the material and installation cost
The most sophisticated option includes
Grave adds: “If you’re in a heavy rain area against tax. And the Code for Sustainable Homes
a smart header tank which not only
(up to 185cm a year in Scotland) you can awards merits for a reduction in mains water
provides both automatic and manual
collect more water - but then it rains more in consumption (the current obligatory level for mains back up but also saves energy on
summer in the north of the UK meaning there social housing is 105 litres per person per day).
pump use (see www.RainDirector.co.uk).
may not be any to ﬁ t anything bigger than a “Private homes will gain in value if potential
6500 litre tank.” purchasers see the house has “green” merits.
Building regs will change in 2010 to make 125
How it works
litres per person per day the standard,” she adds.
Home systems typically use a self-cleaning
ﬁ lter in the top of the tank. Leaves from East Green Energy, supplies, installs and
the ﬁ lter are washed out to a drain, as is the maintains a range of green energy systems.
overﬂ ow of rainwater when the tank is full. Visit www.eastgreen.co.uk or call 01728
Underground water remains cool, so there’s 602315.
no bacterial action and no discolouration of the For details of rainwater harvesting systems go
water. A submersible pump in the bottom of to www.rainwaterharvesting.co.uk
SUSTAINABLE SOLUTIONS April 2009 33
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