1.1 What is rainwater harvesting?
It is the collection from roofs and storage of rainwater that would otherwise flow down gutters into the drain or a septic tank. Rainwater is stored in tanks ranging from 200 litres 20,000 litres, with the most popular for detached family houses at 6,500 litres. The rainwater is not considered potable by the UK Building Regulations but the state-of-the-art filtering provides clear water which is used for drinking in many parts of the world. Water can get brackish if stored above ground where it is subject to summer warmth; digging the tank in underground where the water stays clear, is therefore essential for rainwater to be used in the house for flushing toilets and washing clothes. Your tank kit typically comes with filter, pump and other standard equipment to keep collected water clean. The larger the tank you have, the more money you will eventually save and the more protection you will give your garden during droughts and possible hosepipe bans.
1.2 What can you use rainwater for?
Rainwater can be used for all outdoor uses: watering the garden, washing cars, cleaning patios, drives and windows, topping up swimming pools, ornamental ponds and hot tubs. With some plumbing alterations, it can also be used inside the house to flush WCs and feed clothes washing machines. Besides saving on drinking water use, rainwater use encourages less build-up of calcium deposits in appliances. The diversion of rainwater to the storage tank can in many situations attenuate flooding.
1.3 Why should I use rainwater?
Each person in the UK uses about 160 litres of drinking quality water a day. Nearly half of this amount need not be drinking water. It seems crazy to bring in drinking water from miles away via your water board to water your garden or clean your car when you could provide water directly from your own roof. It is now recognised that the south east of England in particular is short of water (London has less water available per capita than Madrid or Istanbul). April 2007 was the driest on record, but then June 2007 was the wettest on record. That's when the wags started asking when the hosepipe ban would start! The more water you can collect in wet spells, the more you will have when it's dry.
1.4 Is rainwater better than drinking water for outdoor use?
Your garden will prefer rainwater to tap water because it does not contain the chemicals needed to make tap water drinking quality. And when using a cleaning agent, you will need to use much less, again because there are no chemicals and the water is softer.
1.5 How will rainwater harvesting help me during a hosepipe ban?
In 2006 many areas had hosepipe bans banning watering gardens and cleaning cars. New legislation will give water boards the right to prohibit using hosepipes for other outdoor cleaning purposes such as washing boats, patios, drives and windows, and also for filling swimming pools, ornamental ponds and hot tubs.
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1.6 Will I save on my water bill
if I have rainwater harvesting?
You can save on your water bill if you have a meter. Government reports estimate that 70% of customers see their bills reduced with a meter by 10 to 15% because of the user's awareness that mains water costs money. Most water boards have ready-reckoners on their websites to help you decide whether a meter is a good idea. Currently only around 23% of households in the UK have meters, but they are obligatory in new builds. You water board is also obliged to fit you one if you request it.
1.7 If my water is not metered already, can I ask to have one installed?
Yes, all water boards have to install a meter at the request of the householder. Installation is free, and some boards provide the meter as well. Some water boards insist on installing a meter with change of ownership, and sometimes, in tenancy of a property.
1.8 Will I save on my water bill if I have rainwater harvesting?
Typically half your water bill is for mains water supply and half is for drainage. Most calculation of rainwater use for flushing toilets and washing clothes shows that water consumption can be halved. This would therefore knock about 25% off your water bill. In august 2008, 10 water boards applied for price increases that could lead to a 40% rise within 5 years; savings will become more significant.
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2. Planning my rain water harvesting system

2.1 Does the tank have to be underground?
For domestic water use, yes. You should weigh up the
arguments for and against digging your tank into the
ground…
1) in favour of digging the tank in:
a) No unsightly equipment in the garden, especially if
you are installing a tank bigger than 200 or 360 litres
b) Suitable for a small garden or where the space is
otherwise restricted. For example, our stronger tanks
can be installed under a drive way if suitable supports
are constructed over the tank
c) Less risk of brackishness (discoloration due to
bacterial action at 12 degress C and above) in summer
due to warming of the leaf debris at the bottom of the
tank.
d) Negligible risk of frost damage to tank, piping and
pumps in winter. Take into account the prevailing
temperature conditions in winter where you live; if your
pond or water trough freezes up seldom, and if the layer
of ice is only a few centimetres thick at worst, then
your rain water harvesting tank and equipment are
unlikely to be damaged.
2) in favour of situating the tank above ground:
e) Ease of installation and lower installation costs
f) Easier to maintain in case of change of scenario or
pump failure
g) Suitable for farm, outhouse, equestrian, market
garden and other installations where the visual and
aesthetic criteria are less important.
2.2 Do I need a large roof area to provide an
adequate supply of water?
A surprisingly small roof area will give a lot of
rainwater: a typical terraced house with a 6 by 8 metres
roof area could give 30,000 litres a year depending on
the area of the country you live in. Check the
tank size calculator and UK rainfall figures shown
on that page.
2.3 How long would the water last in a drought?
Check the tank size calculator.
You can calculate from the size of your roof and average
rainfall figures in your area (available on our web
site) how much water will come off you roof in a year.
The same calculator works out how long the water will
last in a drought from a) your garden size, b) how much
water you want to give to your plants, and c) the size
of your tank. Aim for between 1 and 4 weeks drought
protection and a tank size which
also suits your budget.
2.4 What else do I need besides a tank?
The filter installed in the pipe to the tank is
essential for larger tanks where water may be stored for
a longer time. It will help prevent water becoming
smelly and discoloured by removing leaves and other
debris. This also reduces the sludge accumulating at the
bottom of the tanks, and reduces clogging of tap
outlets, hoses and watering-can heads. High quality
filters (such as in the turret of the tank) separate
debris out and flush it down the drain or soakaway. Some
downpipe filters eject debris straight out the side,
while cleaned water goes into the tank. Both kinds are
easy to maintain.
For even cleaner water, an overflow siphon collects
smaller particles such as pollen which can accumulate
after filtering on the top layer of rainwater. The
integrated u-bend stops vermin getting into the tank
through the overflow outlet. Where the rainwater flows
into the bottom of the tank, a calming device prevents
the flow from stirring up any silt on the bottom. A
floating intake to the pump takes water from the
cleanest place, a few centimetres below the surface. A
pump maintains a good pressure and flow of water round
the house and garden. Pumps (such as the
Forta Duo and
similar pressure-sensitive pumps) turn on automatically
when you turn on a tap or flush a toilet. It stops on
its own as well. Other less expensive pumps will only
stop when the water level in the tank is too low for it
to work any longer. Although some pumps do have their
own filters, they perform much better if the rainwater
has been filtered already by an exterior filter.
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2.5 Why is it a good idea to install a filter and
pump if I am only using rainwater for the garden?
A filter installed in the down-pipe to the tank, or in
the top of the tank itself, is a good addition for all
tanks but is particularly to be recommended for larger
tanks installed above ground where water may be stored
for a longer time. It will help prevent water becoming
smelly by removing leaves and other debris. This also
stops sludge accumulating at the bottom of the tanks,
and tap outlets, hoses and water-can heads clogging up.
Some filters separate debris out and send it on down the
drainpipe. Other filters eject debris straight out the
side, while cleaned water goes into the tank. Both kinds
are easy to maintain. A pump makes distribution from the
tank easier by maintaining a good pressure. Quality
pumps (such as our
Forta Duo pump) with a
pressure-sensitive switch turn themselves off when water
flow is not needed; when using a spray-head, you do not
have to run in to turn pump off: it will stop when you
click the spray-head to off. Other less expensive pumps
will only stop when the water level in the tank is too
low for it to work any longer.
2.6 What is the best kind of pump to use?
Pumps which switch off when no water is being drawn
(such as our
Forta Duo pump) and which can be used both in and
out of the tank are the best. These allow you, for
example, flexible watering. When using a spray-head, you
do not have to run in to turn pump off: it will stop
when you click the spray-head to off. Other less
expensive pumps will only stop when the water level in
the tank is too low for it to work any longer. If you
order a system with a rain management system which turns
the power on and off to the pump (such as some versions
of the Rain Director) then the
800W StrongArm is our choice.
2.7 What size pipes should I use?
a) Butts and tanks 1000 litres or less, do-it-yourself
systems:
It is tempting to use a small diameter pipe (hosepipe or
25mm (one inch) diameter from the collector-filter to
the tank. However it is worth the effort to use 32mm
pipe to the tank. A narrow pipe will collect the bulk of
water from light rain and drizzle, but during the
critical period of collection, i.e. the summer, you need
to be able to catch the available water which typically
falls in sudden storms at that time of year. So give
yourself a chance by fitting the biggest pipe possible.
In our experience, 32mm is the best. Try to buy usually
Spiroflex or a similar pipe which keeps its shape
(transparent tubing from a DIY shop twists and caves in,
restricting water flow, so avoid it). You can get
Spiroflex from any aquatic or fish pond supplier, often
in the back of your garden centre, or order it from us.
The connection kits are available separately on request.
b) Tanks larger than 1000 litres and all underground
tanks, professional systems :
Rigid drain-pipe is recommended, in either of the two
75mm or 100mm diameter standard sizes, so that the flow
is unrestricted and so that the weight of earth or
backfill does not collapse the pipe. Installations of
this sort would normally be installed by your contractor
or plumber.
In both cases, make the pipe from the tank to the
appliances or garden taps as wide as practical,
certainly not less than one inch (25mm) diameter. 32mm
is preferable to maintain a good flow rate and pressure
for garden sprinkling. Use MDPE pipe with push fittings;
use black pipe not blue to indicate that the rainwater
is non-potable under the UK Building Regulations. Ensure
that the output pipe from a submerged pump is flexible
enough to allow the user to draw the pump out of the
tank (using the cord) for filter cleaning.
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2.8 When do I need to use a filter?
A filter is recommended in every Rain Water Harvesting
installation and essential if the rainwater is going to
be used in the house. It is most critical when leaves
often fall on the roof being used, such as a low roof
with trees nearby.
2.9 What is the best filter to use?
RainWaterHarvesting.co.uk sells three types of filter.
1) The down-pipe filter/collector takes the water feed
for your tank through an outlet in the side; the leaves
or other debris continue down the existing down-pipe
from your gutter. Use this next to the house when
adapting an existing down-pipe. When the tank is full,
excess water flows on down the down-pipe.
2) The leaf extractor filter (e.g. Rainus filter) pushes
leaves or other debris out of the side of the filter and
the clean water continues down the down-pipe. Use this
type on out-houses, garden garages, stables etc when the
down-pipe goes straight into your harvesting tank and
when you don't mind leaves being pushed out the side. 3)
Underground tank kits come with a professional
self-washing filter, like the Optimax Pro, fitted in the
turret of the tank. Leaves are pushed by the water flow
out into the waste pipe.
3) Underground tank kits come with a professional
self-washing filter, like the Optimax Pro, fitted in the
turret of the tank. Leaves are pushed by the water flow
out into the waste pipe.
2.10 Is there a risk that the down-pipe filter will
cause a back-up spill over the gutter?
Both down–pipe filters and leaf extractors have overflow
capacities as big as the original down-pipe to which
they were fitted. You might get back up of water and
overflow at the level of the gutter, but only in such
extreme rain fall that you would probably have had
gutter overflow anyway.
2.11 Why do I need a siphon?
The siphon skims small particles of dirt off the top of
the water by creating a more rapid water flow from time
to time. This is rather like the flush of a toilet but
on a smaller scale. It keeps the water in the tank
cleaner than a plain overflow pipe.
2.12 Can I use a small butt near the house feeding a
larger tank elsewhere?
Yes. You can have a small water butt (say 200 litres)
collecting rainwater off the house down-pipe. As it
fills, an automatic level-sensitive pump sends the water
through an above-ground or buried hose-pipe or 1 inch
pipe to a much bigger storage tank underground or
elsewhere on your property. You should plan for a soak
away to handle excess water at the storage tank.
2.13 What is the best way to distribute water from
the storage tank?
You can:
1) Fill a watering can from the tank,
2) Use hose or tricklers fed by gravity from the tank.
3) Use a level-sensitive pump which stops when the level
in the tank drops to a pre-determined level.
4) Use a pressure sensitive pump which turns off when it
senses back pressure in the pipe it's feeding, e.g. when
you close the sprinkler or tap with which you are doing
the watering.
2.14 Can I use a lawn sprinkler with my rainwater
harvesting tank?
Yes, but you'll empty the tank rather quickly. A normal
movable sprinkler can use 1,000 litres per hour, so a
200 litre tank would be empty in 12 minutes! We
recommend the use of a drip feed system (such as those
from Gardena and Kar) where water is directed to the
roots of the plants at night, controlled by a time
switch. The lawn should be watered with mini sprinklers
for a few minutes daily if required, i.e. consider
fitting a soil humidity gauge.
2.15 Am I obliged to put my water butt on a pedestal
to get the watering can under the tap?
No, if you are going to use a pump. And even without,
attach a short length of pipe to the tap and water will
flow into a watering can or bucket until the level of
the water in the butt is lower than the level you want
in the can.
2.16 Does all rainwater harvesting equipment come
with all the right connectors?
In a word, no. We have been surprised at how lacking in
diligence most of the manufacturers have been in this
respect. Here at RainWaterHarvesting.co.uk we make every
effort to inform buyers what they're getting and we'll
source and provide any extra bits needed. If you buy
hose, try to use 32mm spiral reinforced (25 or 32mm
black MDPE for domestic supply). Flow is better and
connectors easy to get.
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2.17 Can I use rainwater in my pressure cleaner?
Yes but with a suitable pump. Most pressure cleaners,
like the Karcher, need a certain amount of pressure and
flow rate of the water at arrival. We have found that
the small pumps in the £30-£50 range do not deliver
enough pressure, but better ones like the Forta Duo work
fine. Look for 500 to 1100 watts in power and 3 to 5 bar
pressure. Such cleaners use a lot of water so check the
tank level before use (normally by lifting the cover and
looking).
2.18 Can I use rainwater to fill a swimming pool?
Yes. Use an underground rainwater harvesting tank, pump
and filters to ensure that the water being fed to a
swimming pool is well clean. The Building Regulations
are interpreted differently by different council
inspectors: generally it is understood that rain falls
into a swimming pool anyway, so using rainwater properly
filtered provides an even better quality of water. Some
inspectors like to insist on an Ultra-Violet filter
which we can also supply. Check your alkali level and
other water factors after filling with rain water.
2.19 What tank size?
You can
download the tank size calculator from this web site
at or
email us the details and we'll do it for
you. We would need to know the roof area of the
building, its location in the UK, how many people in the
house, how many toilets and washing machines and whether
the water will also be used in the garden
2.20 What advantages do we get under The Code for
Sustainable Homes?
The Code for Sustainable Homes now puts pressure on
builders to install rainwater harvesting in new-builds.
A rating against the Code for Sustainable Homes, which
measures nine categories of sustainable design including
energy, water and waste, will be required for all new
homes. Homes which exceed the sustainable standards in
existing Building Regulations will be awarded up to six
stars. Those homes that have not been assessed against
the Code will score a nil-rating. Many councils are now
giving planning permission only if the development
scores between 3 and 5 against the Code. If you would
like to get a Sustainability Code assessment please
register here and include in
the notes section "Sustainability Code assessment
please.
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3. Using rainwater in the house: domestic systems
3.1 Can I use rainwater in the house?
RainWaterHarvesting.co.uk supplies all the equipment
for domestic rainwater use. Select one of the kits which
include the tank, filter, pump and accessories needed
for such systems. Use of rainwater in the house requires
you to plumb pipes to feed rainwater to the toilets,
washing machine and one or more garden taps. The UK
Building Regulations classify rainwater as non-potable
so use in showers, baths and in the kitchen is not
permitted in the U.K. - even though people in many
countries of the world use stored rainwater for
drinking. Do please check with local authorities about
any other regulations that might apply.
3.2 What size tank do I need?
This depends on five factors; 1) where you live
(amount of rainfall a year), 2) the roof area from which
you can collect water to your underground tank, 3) the
number of toilets and people in the house, 4) the amount
of water you want for your garden and 5) how much
drought protection you want. The tank size calculator on
this website will help you work out your needs and
RainWaterHarvesting.co.uk will check your calculations
for you on request. The majority of tanks sold by us for
a family house are 6500 litres in volume, i.e. the
biggest of the Graf Carat range. If you're fitting a
tank, why not fit the one which gives the best drought
or hosepipe ban protection?
3.3 If I use rainwater in the house, what happens when
my tank runs out?
The automatic mains backup switches in, so you can
go on flushing toilets and washing clothes without
interruption. But you would not be allowed to water the
garden when there is a hosepipe ban if the mains water
is flowing. Remember to specify one of the three mains
water backup options;
a) float switch and solenoid valve on the mains pipe (a
tundish (air gap) is needed to conform with Building
Regs.) (cheapest option),
b) a "rain manager" from various manufacturers with mini
header tank and pump in a large console in your utility
room, and
c) The
Rain Director with microprocessor-controlled roofspace header tank for minimal electricity use, less
pump wear, water during a power cut, auto flush and
holiday modes.
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3.4 What is the power consumption of the "rain managers"
like the Power Rain C or Graf's Silencio?
Nominal working power consumption is 550w with a
surge in power consumption each time the pump starts.
The Rain Director uses about one eighth of the power
because it lets the header tank empty by gravity before
filling it again.
3.5 How loud are rain managers like the Power Rain C?
74 decibel unshielded or 70 decibel shielded. A dull
hum. The Rain Director, on the other hand, makes no
noise in the home because the pump stays submerged in
the underground tank.
3.6 Can I collect grey water with a rainwater tank?
Yes but... Grey water is waste water from the house
(from basins, showers, baths, washing machine and dish
washer) but not toilet wastes and food wastes derived
from garbage grinders (called "black water"). It's
mostly a question of personal taste
whether to use grey water to water the garden, but if
you are not a heavy detergent user, then, yes. Grey
water should not be used to fill swimming pools and it
might give a smeared finish when washing cars. You
should consider a specialist treatment plant (http://www.greywater.com)
and you should also check any applicable regulations. We
do not recommend putting grey water in your rainwater
tank. If you have a big roof and plenty of rain you
might choose not to bother with collecting grey water.
3.7 Is it better or easier to use rainwater than grey
water?
Rainwater is better than grey water as rainwater
contains less detergents, soaps, chemicals and bodily
dirt. But in times of severe water shortage you should
try to store grey water for garden use.
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4.
All about Tank installation
4.1 What are the specifications and dimensions of the
typical tanks?
The vast majority of our sales are of the biggest
Graf Carat tank which has a capacity of 6500 litres. You
can see the
tank manufacturer's brochure by clicking
here
You can see an
engineering drawing of the tank with its
dimensions by clicking here (or substitute the tank size
for 6500 if your tank is other than 6500 litres):
4.2 Why install underground?
a) the low ambient temperature underground in summer
prevents the water getting brackish and discoloured. For
this reason it is not suitable to provide rainwater in
the house from an overground tank.
b) the tanks are big and ugly... not what you want in
the garden from an aesthetic point of view.
4.3 If I buy a kit, what is included?
The best way to purchase rainwater harvesting
equipment is in kit form, i.e. with all the parts
supplied to make a complete system. Our domestic water
kits include not only the pump and filters but also one
of the three types of mains backup;
a) float switch and solenoid valve on the mains pipe,
b) with a rain manager with built in pump and mini
header tank in one unit and
c) our new Rain Director® with smart header tank and
computerised control panel.
More
Rain Director®
information can be downloaded here or a
Rain Director® manual here.
4.4 What is not included in the kit?
Your contractor needs to supply the piping to
connect
a) gutter to tank (usually 4 inch gutter down pipe),
b) the piping from tank to the house (MDPE black 32mm
(1.25 inch) with BSP push fittings) and
c) the internal piping to the appliances.
4.5 What building regulations are applicable?
The client is responsible for complying with
applicable regulations which can be interpreted
differently in parts of the country. Most building regs
for domestic use of rainwater require that a device must
be fitted which prevents backpumping of rainwater into
the mains system such as a tundish at the outlet of the
mains to the tank.
4.6 Where should the tank be?
The tank should be located convenient to a point
where the downpipes from all four sides of the building
can be brought together in one 110 mm drain pipe. This
is usually the lowest point in the grounds if there is
any slope. The pump will then draw water from the tank
up to any point in the building. It should join the
internal rainwater piping network in a utility room or
the point where the mains water arrives in the building.
4.7 Can we use water off the drive and patio?
We would not recommend using water off the hard
standing or patio because oil spills or other waste
could enter the water destined for washing clothes and
flushing toilets. Some clients use a separate tank for
run-off (and grey water) and this water is used on the
garden only.
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4.8 What are the installation requirements for a large
underground tank?
a) It is essential you follow the manufacturer's
instructions for fitting or the guarantee will be void.
The
installation instructions of a typical kit
may be downloaded here
b) If the ground where the tank is to be installed is
well drained and has a low water table, back filling
with sharp sand, earth or pebbles is OK. You are advised
by the tank manufacturers to provide a concrete base of
150mm under the tank.
c) If the ground is habitually wet or the water table is
high, there must be a beam or concrete to prevent the
tank when empty from popping up out of the ground. Yes,
it happens. Alternatively, drain the area directly
around the tank with a pump if needed.
d) MDPE tanks are not normally strong enough to keep
their shape in compression so the tank must be filled
with water as you proceed with backfilling.
4.9 I have a low-lying garden where water collects. Can
I get it drained?
Yes, use a dirty water pump with float switch from
our range. Make a culvert or manhole at a low point in
the garden into which surface water will flow. The pump
starts automatically when water is present; you can
route the outlet pipe up to a drain or soakaway.
4.10 Our rainwater tank is going to be so low that the
overflow and leaf output have nowhere to go. What do I
do?
It is vital that the rainwater flows smartly over
the filter in the turret of the underground tank so that
leaves and debris are flushed away. If the top of the
tank is lower than the drain then you need one of two
solutions. 1) Make a soakaway with enough capacity to
take both the excess water off the roof (tank full) and
the leaves and debris. 2) Make a manhole beyond the
outlet into which leaves and debris will flow. Use a
plain mesh filter to keep the leaves on one side so that
you can manually extract them from time to time. Beyond
the mesh your soakaway absorbs the excess water. An
optional pump in the clean side of the manhole starts
automatically when water is present; you can route the
outlet pipe up to a drain or soakaway.
4.11 How do I get the submerged pump out for filter
cleaning and maintenance?
Ensure that the pump has been installed with its cord
(supplied with most pumps) attached both to the pump and
to a point at the top of the tank. Ensure also that the
output pipe from the pump is flexible enough for you to
be able to pull it out of the tank. If the pump is
fitted with a basket filter, clean it out. There are no
other serviceable parts
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5. Use of rainwater in the garden
5.1 Does my tank provide enough water to sprinkle the
lawn?
In a word, no. A sprinkler uses about 1000 litre an
hour, so even if you use a large 6500 litre tank, it
would be empty in a morning. We recommend the use of a
trickle feed, soaker hose or irrigation system
5.2 What Irrigation system should I use?
If you are watering flower beds and individual plants,
then a leaking or soaker hose is the most water
efficient. The water goes straight into the ground where
it is needed. A typical leaking pipe uses 1 to 10 litres
per metre per hour depending on whether it is 4mm or
12.5 mm diameter. Drippers (trickle feed) are water
efficient also, directing water exactly to where water
is needed. Fixed rate drippers use 4 litres an hour per
dripper. Mini-sprinklers can be directed to specific
areas and plants typically vary in range from 1.5 m, 2m
and 3m, and use on average 55 litres per sprinkler per
hour. For example, a 40 sprinkler kit covering 750 m2
would use @ 2200 litres an hour. A typical spray
sprinkler covering 240 m2 may not cost very much (eg
£12.99) but is not water efficient, using @ 1000 litres
an hour. To water 750 m2 would therefore use @ 3000
litres an hour, nearly a third more than the
mini-sprinkler system.
5.3 How much water should I use and how often during
a drought?
The Royal Horticultural Society says that “up to 24
litres per square metre every 7-10 days will be
sufficient to maintain plant growth” (ie 2.4 litres a
day) or “2.5 cms of water per plant every 10 days during
dry spells”. For example, running a sprinkler system for
2 or 3 minutes every 24 hours should be enough during a
dry spell. This is only a guideline as the water need
will vary with the size of the plant.
5.4 Can I attach a hose to the pump in the
underground tank?
In principle yes, but we recommend that the hose off the
pump is a one inch (25mm) or larger pipe as far as a
connector or stand pipe tap. This is because water
flowing in the constriction of a half inch hose means
that you do not get sufficient pressure and flow rate at
the far end.
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6. Maintenance
6.1 Do I have to clear the leaves out of the filter?
No. The
Graf Optimax filter in the turret of the
underground tank, and those from other manufacturers
which are not basket filters, feature a
nearly-horizontal mesh filter from which the leaves are
washed away by the arriving rainwater. Ensure when
installing the tank that the debris outlet (which
doubles as the tank's overflow) has enough drop to
ensure a good flow of water away from the filter towards
the soakaway or drain.
6.2 Doesn't leaf debris or sediment get into the stored
water?
As small amount, yes. Most tanks accumulate a
millimetre or two a year, but there are 3 further
devices in our kits which ensure clean rainwater in the
home.
a) The calmed inlet prevents arriving water from
disturbing and silt.
b) The siphon on the overflow sucks dirt of the surface
of the water
c) The floating intake takes rainwater for the house
from just below the surface of the water, where it's
clean.
6.3 Should I clean the sediment out?
The tank manufacturers mostly say you should inspect
the tank for silt build-up every couple of years, but it
can be much long before any intervention is required. To
get the silt out, lower a dirty water pump to the bottom
of the tank when it's nearly empty and pump out the silt
with the remaining water. A hose or pressure washer
could also be useful.
6.4 Are the tanks guaranteed?
The Hercules and Carat tanks from Graf are
guaranteed 15 years.
6.5 Does the pump need maintenance?
The pumps in the £200 range are strong and
long-lasting. They require no maintenance and, being
submersible, there are no user-serviceable parts. In the
case of breakdown the pump can be pulled out with its
cord (the top of which is attached to the inside of the
tank turret at installation) and replaced. Check with
your supplier about the guarantee involved.
6.6 Is there a way of reducing pump wear?
Yes. It seems un-necessary for the pump to start off
pumping every time a toilet is flushed, especially
because a disproportionately high amount of electricity
is used when the pump starts, and because the pump, in
simple installations, goes on pumping for some time
after it stops supplying water. The Rain Director solves
these problems. Its microprocessor-controlled roofspace
header tank uses about 8 times less electricity, wears
the pump less, provides water during a power cut, and
has auto flush and holiday modes.
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7.1 Can I make my rainwater into drinking water and
what about council approval?
The UK Building Regulations specify rainwater as
non-potable water. But if you get the water tested and
fit the right equipment you can use your rainwater all
over the house even for drinking.
The UK Government's requirements are at
http://www.opsi.gov.uk/SI/si2000/20 003184.htm.
It's quite a read.
The WHO's recommendations are at
http://www.who.int/water_sanitation _health/dwq/gdwq3rev/en/index.html
In practice, it is vital to get water tested if the
users or authorities want to be certain of its quality.
There are testing companies all over Britain and one can
identify them locally when required. Most council
inspectors will want to see test results and a
confirmation from a supplier that the equipment will
handle whatever might be polluting the water. The most
common pollutants and their remedies are as follows: