ITHOUT water, life comes
to an end. Although that
is a dramatic statement,
it is very true that
anything organic will cease to exist
without a source of water. Animals
suffer, anything green withers, and we
humans start to smell like that guy you
were standing behind at the dairy the
other day.
There are several fundamental
building blocks in the creation of the
rural dream. A cornerstone is water.
There are several different scenarios
to water collection and distribution
that we will cover off in this article harvesting, storing and utilising.
Harvesting water
Rainwater is commonly used
in a rural environment, due to not
having town supply available and its
relative cost-benefit to putting down
a bore. Rainwater is cheap, easy
and fairly reliable. Unfortunately, as
roofs (your rain water catchment) are
exposed to the environment, they
become contaminated by infiltration
of all types. Bird droppings, rotting
vegetation, pollen, dust and even the
odd rodent or bird can make your tank
or guttering its watery grave.
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Ideally you don’t want these
contaminants making there way into
your water supply.
There is a huge array of products
available to mitigate or even eliminate
these contaminants from your
water. Leaf diverters are a common
and cheap first step. This is a simple
device with an angled mesh plate that
sits in a downpipe and lets larger
foreign objects fall out the side of the
downpipe, while the water carries on
through and into the tank. Another
great invention is the first-flush
diverter. This is a cylindrical device
in the down pipe with a floating ball
inside and a small outlet at the bottom.
As the first rain comes through and
washes any dust and dirt off the roof,
it fills the cylinder until the ball blocks
off the inlet. Once the inlet is blocked
off, the rain then starts filling your
tank. All going well, the rain water
is now free of contaminants, since
the initial dirty water was diverted
away from your drinking supply. A
quick Google of “rainwater harvesting
products” will get you started.
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Photographs: Jamie Lunnam, Sales Manager, Devan
W
When it rains it pours
By Jamie Lunnam, Sales Manger, Devan
If you are looking to put down
a bore, there are a lot of questions
about cost (which relate to the depth
of the bore) and water quality. The
water you may be able to get from a
bore may only be suitable for animal
water and non-potable uses. An expert
in the field will need to be advising
you on the ins-and-outs of this.
Although spring water is often a bit
more straight forward, an expert is still
required to advise you on quantity and
quality matters. Do your homework on
reputable contractors who specialise
in water in your area, and they should
be very helpful and inexpensive to
get preliminary advice and assist with
testing etc.
Storage types
There is only one secure way to
store water and that is with a tank of
some description, however there are
many different tank options available
today. Concrete tanks were once the
number one option and are still very
popular. Concrete tanks are more
expensive than other options and have
size limitations if being transported by
road. In saying this, they have other
benefits including being a little more
forgiving of installations that are not
perfect. A common misunderstanding
is that concrete tanks can be buried.
This is only true if it is a concrete
tank that is designed and built to be
buried. These tanks have a column
in the centre of the tank to assist
in strengthening the tank so it can
cope of the forces involved with being
below ground level.
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Polyethylene (plastic) water tanks
have surged to the fore as the most
popular water storage tank over the
last 20 years. Although they are not as
rigid as concrete tanks, plastic tanks
are super-strong and do not fade,
crack or break down over time. Many
tank manufacturers provide a 20-year
guarantee on their large water tanks,
which should help in dispelling any
myth that they are not as strong as
concrete tanks. Plastic water tanks are
a cheaper option that allow a large
volume tank to be easily transported
to site (up to 30,000 litre tanks can
be transported on their side without
being oversize) and they are relatively
light, which means they are much
easier to man-handle into place on
site.
Storage requirements
When selecting a tank the first
question a lot of people want an
answer to is what size tank they need.
Obviously there are a lot of variables
involved in answering this question.
First of all you need to know how
much water you will be consuming,
and therefore how much you need to
have available.
Now you have an idea of how
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When it rains
it pours
Source: www.lifestyleblock.co.nz
Key usage data for calculating your
likely consumption is detailed below
Consumer
Litres per unit per day
Household use per person
Cattle (lactating)
70
Cattle (dry)
45
Calves
25
Horse (working)
55
Horse (grazing)
35
Sheep
4
Lambs
1
Sow
25
Poultry
0.2
much water you will need per day, you
can assess your storage requirements
based on how you are going to source
your water.
Trickle feed, bore or spring supply:
If you are getting your water from one
of these sources you only need to store
enough water for daily consumption
and maybe some for emergency supply
because the supply is continuous. You
need to find out what rate the water
is being delivered to your storage to
ascertain how much capacity you need
based on the approximate figures
above. As the supply is continuous
and generally reliable, you may only
need a 5000-10,000 litre tank, but the
bigger the better.
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■ 500m3 roof (example house and
shedding) X 87mm (average March
rainfall in Hamilton) will make 39,150
litres available for the month of March
(based on mean data from Niwa)
Comprehensive rainfall details
for New Zealand are available at
www.niwa.co.nz
If we consider a full working
example of a lifestyle block in Matangi,
Hamilton:
Two adults and
three children 1000L per day
Rainwater harvest
If you want to know how much water
you will be able to harvest from your
roof, there is a quick calculation you
can use:
■ Roof area (in metres) x rainfall (in
millimetres) X 0.9 (to accommodate
loss) = approximate litres of water
containable
You could apply this over the
annual rainfall in your area:
■ 500m3 roof (example house and
shedding) X 1190mm annual rainfall
(Hamilton) X 0.9 = 535,500 litres of
water available for an average year
Or you could apply this on a
monthly basis to test required short
term capacity:
Two grazing
steers
80L per day
One sheep
4L per day
One horse
35L per day
Total daily
requirement
1119L per day
Total monthly
requirement
33,570L per month
Based on this data, you would
need a capacity of 34,000 to meet your
minimum consumption, however this
does not accommodate any margin for
emergency or prolonged dry spells.
A common combination in this type
of arrangement would be 2 x 25,000
litre tanks providing ample capacity
to catch as much rain as possible
and allow for an extended dry period
without too much cause for concern.
If money is a bit tight, you could risk
having one 30,000 litre tank, being
frugal with your water consumption,
and if need be, you can buy in a tanker
of water in emergencies.
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Using your precious water
To make use of your water there
are two basic options – gravity or
pump. A gravity fed system is fine for
the likes of stock water and in older
less-demanding homes. In a modern
home that has multiple bathrooms,
dishwashers, irrigated gardens and
endless hot water, a pumped system
is essential if you want to maintain
an uninterrupted supply with decent
pressure. Your installer will be able
to make recommendations on what is
going to work best for your block, and
the demands on it.
Pump selection should not be taken
lightly, as it is an integral component of
your operation. Good-quality pumps
are not excessively priced and will go
the distance.
It is a good idea to have some form
of level indicator installed on your
water storage tanks. These devices take
many forms from the clearly visible
over a long distance, to indicators
that run up and down the side of the
tank. There are also electronic devices
available, so you can have a read-out
on a small screen in the home.
When it comes to consumption of
water within the home (potable water
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supply) it is necessary to have the water
going through some filters to remove
any remaining organic material. There
are many companies specialising in
home water supply filtration that will
present many options depending on
the quality of the water to be treated,
and the desired quality of the end
product. From basic inline filters (a
few hundred dollars) through to UV
filtration ($1000 and upwards) there is
a solution to any need.
This article only really covers over
the basics to consider before you seek
further professional advice. Although
some handy people will be perfectly
capable of installing a simple system
to catch water off a barn roof to feed
troughs, it is advisable to engage
experts when things get a bit more
serious. Reticulating water throughout
a working block is a critical link in
your operation and should not be
taken lightly. A well-planned system
with quality components will see your
block well-watered and trouble-free
for a long time.
Devan Tanks has been in
the water storage business for
decades and its staff have all
the answers to many questions.
Call Devan on 0800 244 503 for some
no-obligation brain-picking.
LF
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