Tank
Water Care
The
following summary is from:
dhs.sa.gov.au
(pdf file)
Other good links and interesting ideas about water collecting:
.gardenweb.Need
cheap ideas for rainwater collection.
sorell.tas.gov.au
Howto Live on Tank Water
waterproofingadelaide.sa.gov.au/
Browse submissions
www.rainbarrelguide.com
How to use rain barrels for water collection
In
Australia the use of domestic rainwater tanks has a long history.
A 1994 survey by the Australian Bureau of Statistics showed
that about 13% of all Australian households use rainwater
tanks as a source of drinking water. The highest use was in
South Australia (37%) and the lowest was in the Northern Territory
(2%) and the Australian Capital Territory (0%).
The 1994 survey also showed that the use of rainwater tanks
was far more
common outside the capital cities with 30.4% of rural Australians
using rainwater compared
to 6.5% in the capitals (Australian Bureau of Statistics,
1994).
These figures will be no doubt changing as Australians become
more and more aware of the need to conserve water resources
and recent government initiatives to save water.
It
is important to make sure your tank water isn’t contaminated.
Sometimes people consider tank water to be more ‘natural’
or cleaner than mains supplies and therefore leave it untreated.
However care needs to be taken to ensure this water is as
good, if not better, than other options which may be available.
Some
water supplies will need to be disinfected.
People with suppressed immune systems should only consume
water that has been boiled or otherwise treated and tested.
Contaminated
water can make you ill.
The thought that rainwater is safe to drink is probably
true if it is clear, has little taste or smell and importantly
that the source of the rainwater is a well maintained tank
and roof catchment system.
Rainwater collected and stored in domestic tanks is likely
to contain micro-organisms from one or a number of sources.
While most will be harmless the safety of rainwater will depend
on the exclusion of organisms that can cause infections of
the gastrointestinal tract (enteric pathogens). The enteric
pathogens include types of bacteria, viruses and protozoa.
These organisms are introduced into drinking water supplies
by contamination with faecal material from humans, animals
and birds.
Your
tank water can be contaminated by a variety of things:
• Animal faeces - like bird or animal droppings on the
roof.
• Human faeces - leaking from septic systems or waste
water drainage.
• Pesticides - in runoff from farms, or blown onto roofs.
• Arsenic and heavy metals - in soil from industrial
or mining sites.
• Dust - containing chemicals may be blown onto your
roof.
• Air pollution - runoff from roofs in urban and industrial
areas may contain chemicals.
• Lead - from old paint or flashing on roofs can flake
and end up in tanks.
• Algae - including toxic blue-green algae which are
not destroyed by boiling.
Collect and store your water carefully.
If you collect and store your water carefully, you can reduce
the risk of contamination.
You should:
• Make sure surface runoff and leakage from sewage pipes
and other drainage cannot enter your water storage.
• Seal your water storage so animals, birds and sunlight
cannot get in.
• Collect water only from clean roofs - not from those
painted recently or painted with lead-based paints or coated
with tar.
• Clean your roof, gutters and water tanks regularly.
• Install screens or filters between the supply and
storage.
• Install a 'first flush' diverter - the first rain
after a dry period contains most of the contaminants.
What
to do if there's a dead animal in the tank
Where a rainwater tank has become contaminated by a dead animal
such as a bird or rodent, carefully remove as much as possible
of the animal carcass and then disinfect the water. If the
animal is large such as a possum or cat and badly decayed,
the taste of the water will probably be affected. It is recommended
that the tank be drained and cleaned as soon as possible.
The point of entry for the animal should be located and repaired/sealed.
Roofing
materials
Roofs may be constructed from a variety of materials such
as cement or terracotta tiles; Colorbond, zincalume and galvanised
steel sheeting; asbestos/fibro cement; polycarbonate or fibreglass
sheeting; and slate. Regardless of the roofing material used,
with new roofs it is advisable to divert the first few substantial
run-offs away from the rainwater tank. This is done to allow
dust and other debris left on the roof after construction
to be washed away.
Where concerns exist about the suitability of a roofing material
for use as a rainwater catchment surface, advice on the matter
should be sought from the manufacturer.
Asbestos/fibro-cement
roofing
Although no longer used in new houses, asbestos cement may
be present in some older type roofs (pre 1970s). Although
asbestos fibres are dangerous to health when inhaled in sufficient
quantities, it is not believed that asbestos in drinking water
poses a risk.
Roofing material should be left undisturbed as far as practicable
since asbestos fibres, while bound securely in fibro-cement
sheeting, can be released into the air by actions such as
cutting, grinding or drilling. High pressure roof cleaning
methods should also be avoided.
Where the roof catchment area has deteriorated badly it should
be replaced with asbestos-free substitutes.
Cement
based or terracotta tiles
The coloured surface of cement based or terracotta tiles will
oxidise over time through natural weathering. This oxidised
coating may break down slowly and be washed into rainwater
tanks, thus colouring the water.
The coating has been found to be non-toxic and, if left undisturbed,
will settle to the bottom
of the tank.
Paints
and coatings
Before purchasing materials or paint to be used on roofs that
will be used to collect rainwater for drinking, read and observe
the manufacturer’s recommendations on labels and brochures.
Look for warnings. If in doubt check with the manufacturer.
Lead-based paints (including primers) - are toxic
and not suitable for use in association with the collection
of rainwater for human consumption.
Acrylic paint - will leach dissolved chemicals including
detergents in the first few run-offs after application and
these run-offs should not be collected.
Bitumen-based (tar) materials - are generally not
recommended as they may leach hazardous substances or cause
taste problems.
Lead
flashing
Lead is a cumulative poison that can have a number of adverse
effects including serious impacts on the central nervous system.
In utero exposure of fetuses and exposure of infants are of
greatest concern.
As a precaution lead flashing should not be used on those
parts of a roof used as a rainwater catchment area. In the
case of an existing roof, lead flashing should be replaced
if possible. Where small quantities of lead flashing are used
or retained it can be painted over with a suitable roof paint.
Coated lead flashing is also available.
Airborne
contaminants
There is an increased risk of pollution by airborne contaminants
in major urban centres and industrial areas. Collection of
rainwater for human consumption (drinking and cooking) in
areas affected by heavy traffic, industry, incinerators and
smelters is not recommended. When in doubt about the possible
impact of local industry advice should be sought from the
local authority, environmental health authority or environment
protection authority. Although the use of pesticides is coming
under increasing scrutiny and control, rainwater collected
in some agricultural areas may be subject to contamination
by pesticides or other chemicals. Aerial spraying provides
a greater potential for contamination.
Wood
heaters
There have been consumer reports of contamination, including
tainting with creosote, of rainwater collected from roofs
that incorporate flues from wood burners. A range of hydrocarbons
could be deposited on roofs in the vicinity of such flues
It is suggested that where possible rainwater should not be
collected from that part of a roof that incorporates a flue
from a wood burner. In addition extra care should be taken
to operate wood burners correctly and to only use apropriate
fuel.
Tank
materials
Rainwater tanks are available in a range of suitable materials
including galvanised, Aquaplate or zincalume steel; fibreglass;
plastic; and concrete. Australian and Australian/New Zealand
Standards apply to tanks and their associated fixtures and
Fittings.
Wherever possible materials complying with the appropriate
Australian or Australian/New
Zealand Standard should be used
Steel
tanks
Galvanised steel is not resistant to corrosion but it is available
with rust resistant coatings such as zincalume or Aquaplate.
The initial corrosion of galvanised steel normally leads to
the production of a thin adherent film that coats the surface
of the tank and provides protection against further corrosion.
It is important when cleaning such tanks not to disturb this
film.
New tanks may leach excess concentrations of zinc which could
affect the taste of stored rainwater. These tanks may need
to be flushed before use.
Aquaplate steel has a food-grade polymer skin complying with
the requirements of Australian Standard, AS 2070, bonded to
a corrosion resistant galvanised steel base. A number of precautions
need to be taken with tanks manufactured using Aquaplate:
-
the polymer coating is not resistant to prolonged exposure
to sunlight and tanks made of Aquaplate must have a top
cover in place at all times;
-
kerosene
or similar chemicals used as mosquito larvicides can lead
to the degeneration of the polymer coating and should
not be used in these tanks;
-
the
polymer coat should not be damaged when cleaning or installing
the tank. If the coating is damaged, it should be repaired
immediately using an appropriate sealant to prevent corrosion
of the metal portions of the tank.
Copper or copper alloy fittings (brass and bronze) should
not be connected directly to steel tanks as this causes corrosion.
A minimum of two metres of plastic pipe suitable for potable
water should be used between the tank and copper fittings.
Concrete
tanks
Concrete and ferro-cement tanks are strong and long lasting
and can be installed underground. New tanks may impart tastes
and may leach lime thereby increasing the pH of water. Accordingly
these tanks may need to be flushed before use.
Fibreglass
tanks
Fibreglass tanks suitable for the collection of rainwater
are available. These tanks are manufactured with a food-grade
coating on their interior surface. The coating is cured before
the tanks are offered for sale. The tanks should also be manufactured
in a manner to prevent the entry of light which could encourage
algal growth.
Plastic
tanks
Increasing ranges of tanks manufactured from synthetic polymers
are becoming available. Plastic tanks and plastic liners should
be constructed of materials that are at least of foodgrade
standard (AS 2070) and preferably that comply with the requirements
of Australian Standards. As with fibreglass tanks, the tanksshould
be manufactured in a manner to prevent the entry of light.
Regulations
Before purchasing or installing a rainwater tank it is important
to establish whether there are any local health, building
or planning regulations associated with rainwater tanks. The
local council or regional authority with jurisdiction over
these regulations should be consulted. Water authorities do
not allow direct connection of rainwater systems with reticulated
water supplies or alternatively require the use of backflow
prevention devices to stop rainwater siphoning back into the
reticulated supply. If in doubt information should be sought
from the local water authority.
Underground
tanks
Underground tanks require additional protection against entry
of surface run-off or groundwater, animal or human faecal
material and soils. These tanks need to be properly sealed
and access points need to be protected against surface run-off.
Maintenance and cleaning of underground tanks may be more
difficult.
Keeping
out pests
Tanks should have impervious covers and all access points
except for the inlet and overflow should be provided with
close fitting lids which should be kept shut unless in use.
Mosquitoes
Rainwater tanks provide very good places for mosquito breeding.
The most effective control measure is to prevent access of
adult mosquitoes.
The inlet to the tank should incorporate a mesh covering and/or
strainer to prevent the access of mosquitoes and other insects
and to prevent material such as leaves etc that may have collected
on the roof or in gutters from being washed into the tank.
The overflow should also be covered with an insect-proof mesh.
Rainwater tanks can provide good habitats for mosquito breeding.
The most effective control measure is to prevent access of
adult mosquitoes. If access has occurred remedial action can
be taken to prevent the release of mosquitoes.
Ensure that unless in use all access points excluding the
inlet and any overflows are kept shut with close fitting lids
that will prevent access of mosquitoes. Inlets and overflows
should be covered with closely fitting removable insect-proof
screens. The screens should be readily accessible for regular
cleaning.
Mosquito larvae (wrigglers) found in rainwater tanks indicate
the presence of an opening through which the female mosquito
can enter and lay eggs on the water. The opening should be
closed. This will prevent further entry and will also prevent
the escape of any hatched mosquitoes.
Larvae present in rainwater can be treated by the addition
of a small quantity of domestic kerosene (5 mL per 1000 litres).
Commercial or industrial kerosenes (eg power kerosene for
tractors etc) should not be used for mosquito
control. Kerosene should not be used in tanks coated with
Aquaplate. In addition, kerosene may not be suitable for use
in tanks constructed or lined with plastic. If in doubt consult
the manufacturer.
Used carefully kerosene will not provide any risk to human
health but excessive amounts can taint the water and it is
a human poison. Kerosene should not be added when water levels
are low. Kerosene added to the surface will not mix through
the body of rainwater in the tank and it will either be washed
out of the tank by overflow or it will evaporate.
Light
Tanks should be light proof to minimise algal growth. Most
algae will not make water unsafe for human consumption but
can adversely affect the taste, odour and appearance of the
water.
First
flush
After any dry period it is good practice to let the first
run-off of rain bypass the tank. This first rain will wash
the roof catchment and may contain higher than average amounts
of accumulated dust, bird and animal droppings, leaves and
other debris. It has been shown for small roofs that the water
quality improves once the first 5 litres of water has passed
through the down-pipe from the roof guttering. For an average
roof catchment it is suggested that the first 20-25 litres
should be diverted/discarded.
First flush diversion devices are available and the installation
of such a device should be considered as a means of improving
water quality collected in tanks.
Overflow
Run-off that is not collected in the tank or that overflows
should be diverted away from tank foundations, buildings or
other structures. This water should be directed onto gardens
or into the stormwater drain; it should not be allowed to
pool or to cause nuisance to neighbouring properties or to
areas of public access. Local authorities have regulations
or requirements that apply to diverted or excess rainwater
flows.
Inlet
Wherever possible all sections of inlet pipes should be directed
down and rainwater should flow into the top of the tank. The
inclusion of rising sections will provide potential traps
for sediments, biofilms and stagnant water and these should
be avoided.
Roof
protection
Roof catchment areas should be kept clear of overhanging vegetation
to reduce the amount of leaves and debris falling onto the
catchment area. Overhanging branches also provide access to
the roof for rodents, cats and possums and can provide roosting
points for birds. Gutters can be shielded from large debris
(bark, larger leaves, etc) with plastic mesh but smaller particles
will still accumulate and require regular removal.
Appliances
on your roof
Overflow, discharge or bleed-off pipes from roof-mounted appliances
such as evaporative air conditioners, hot water services,
and solar heaters should not discharge onto the rainwater
catchment area.
Maintenance
The primary focus of maintenance procedures should be to keep
all components clean and to minimise the risk of contamination/rubbish
either entering or remaining in rainwater tanks Inlet screens
and first flush/bypass devices should be cleaned regularly
and kept in good repair.
Sludge may be removed by siphoning without emptying the tank.
To do this, use an inverted funnel in the end of a hose and
move it carefully across the bottom of the tank. The sludge
plus the lower portion of water in the tank can then be released
to waste. If leaves and coarser debris is present in the sludge,
a siphon hose of approximately 50 mm diameter should be used.
Sludge may also be pumped from the tank with minimum loss
of water by using a suitable motor operated pump and attachments.
Finally sludge can also be removed by draining and cleaning
the tank. If a drain plug is provided at the base of the tank,
water can be run to waste to discharge the sludge. Once the
tank is empty, the remaining sludge can be scooped up and
removed through the access opening. Care should be taken not
to disturb the protective film on the inside surface of steel
tanks.
When
entering a tank, care should be taken to ensure adequate
ventilation is provided and an additional person is in attendance.
Advice on working in
confined spaces should be available from Occupational, Health,
Safety and Welfare
authorities in each State and Territory.
Regular
disinfection of rainwater held in domestic tanks is not considered
necessary in most cases and is generally only recommended
as a remedial action. In the absence of any known problems
and if the water is clear, essentially odourless and does
not contain any suspended material it is unlikely to cause
illness in most users. However, the microbiological quality
at times may not be as good as reticulated water supplies.
For those with lower immune responses such as the very young
or very old, cancer patients, people with diabetes, organ
transplants or those who are HIV positive, boiling the water
before consumption should be considered. If gastric upsets
are being experienced, boiling should also be considered.
If the tank water is suspected as being a possible cause of
gastric illness then the rainwater tank and catchment area
should be inspected and any appropriate remedial action should
be taken. If the water is coloured or smells the catchment
area and tank should be inspected and appropriate remedial
action should be taken to remove the source of any problems.
If the rainwater is the only source of water it should be
filtered or boiled. The tank should be drained and cleaned
at the first opportunity. Where rainwater is the secondary
source of water, the tank should be drained and cleaned prior
to the next rainfall.
Rainwater
can be disinfected by heating and holding at a rolling boil
for one minute or more (CDC, 1995, 1997; WHO, 1994). This
will kill any harmful bacteria, viruses or protozoa including
Giardia and Cryptosporidium.
The water can then be cooled and stored in a clean container
until use. To improve the taste of boiled water, pour it back
and forth from one clean container to another, or let it stand
for a few hours to increase the dissolved oxygen concentration.
In some cases UV disinfection has been used to treat rainwater
supplied through internal house taps. While this form of disinfection
could be quite effective for rainwater it should not be used
as a replacement for proper maintenance procedures.
If water filters are installed they should be maintained exactly
to manufacturers’ specifications to avoid problems associated
with microbial growths.
From:
dhs.sa.gov.au
(pdf file)
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