FEATURE
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1731:2017 mark. The broader market should also
know that not all plastic tank manufacturers are SANS
1731:2017 compliant and that it is in their best interest
to purchase tanks that carry the SANS mark,” Wiid says.
PRODUCT QUALITY
The quality of water storage tanks is important because it
impacts on the quality of the water stored in them, while
their durability is a key attribute. Water storage tank
quality depends on:
• thermal insulation to deter bacterial growth;
• UV-ray protection to reduce sun damage; and
• Opaque and not transparent material to inhibit
algae formation.
Brink says the temperature in a storage tank must
not reach more than 23°C to prevent the growth of
legionella; tanks standing in the sun must therefore
be protected from getting too hot. “Water storage
tanks made in the process of rotational moulding
are stronger and can be manufactured faster and
cheaper,” says Telford.
TREATING STORED WATER FOR APPROPRIATE USE
Brink warns that the risk associated with using grey
water and rainwater is very high and it should not be
done without proper knowledge and treatment, as
well as marking the piping and all the other important
technical items.
“Black water is not allowed to be treated on the premises
of any building, unless it has no sewer connection. Only
seven regulations exist for drainage and the first one
states that if a sewer connection is available, it must
be used. Treating black water on site is expensive and
carries a high risk, which requires skilled management
24 hours a day.” He agrees that it is important to use
alternative water but emphasises that users cannot be
exposed to the risk without a proper standard. Telford
says it is important to know the difference between
rainwater and grey water to treat it appropriately.
“Rainwater contains organic matter, such as leaves and
bird droppings from the roof, while grey water contains
some chemicals, such as detergent or soap. Black water,
www.plumbingafrica.co.za
The ARMSA/SANS-approved
sticker used on tanks that
comply with the standard.
Calcamite
AVAILABLE SOLUTIONS
Plastic water storage tanks are usually used to keep
water for daily use in homes as well as for commercial
and industrial operations, such as firefighting reserves,
agriculture, irrigation, chemical manufacturing, food
processing, and the reuse of wastewater. “These tanks
can be used to store rainwater captured from roofs
during a downpour, or grey captured by connecting
tanks to outlets such as shower drains and washing
machines,” Telford explains.
A basic grey water system.
on the other hand, contains organic waste and includes
sewerage and water from dishwashing.”
Rainwater can be used to flush toilets, wash clothes,
water gardens, and even drinking after it is filtered to
remove any organic material. Grey water can be used
to replenish toilets and run washing machines, but it
cannot be used for drinking and cooking, depending on
the chemicals in the water. Washing machine water can
be used on lawns, but may not be ideal for pot plants or
vegetables, although shower water can be used for this,
Telford explains.
How grey water is treated before use depends on what
it will be used for, says Telford. “If the water will be used
to water vegetables, it must be treated to ensure th e
plants do not absorb chemicals and salt, but less caution
is required for other plants. Grey water from a bath or
shower will contain fewer chemicals, but grey water
must be filtered to create drinking water. No treatment is
required for grey water if it is used to flush toilets.”
Grey water cannot be stored, unless it is treated first,
because the kind of organic matter in the water is
unknown. According to Telford, the organic matter can
grow quickly and spread in a tank, while some types
of detergents and chemicals can also encourage the
growth of organic material, such as algae, which can be
poisonous or damage tanks and pipes.
INCORPORATING PLASTIC WATER STORAGE INTO
AN EXISTING SYSTEM
Telford says it is better to buy a ready-to-use system
than trying to install a do-it-yourself job, to avoid using
incorrect fittings and seals. “Only SANS 10400 tanks and
SABS-approved fittings should be used for waste water.”
He says SANS 1732 will hopefully deal with all these
issues when it is published, but it might still take a few
years before it is accepted and launched. PA
“The question
is, why are
there no
appropriate
standards for
grey water
and rainwater
harvesting and
domestic water
in buildings?”
Vollie Brink, wet
services engineer
May 2018 Volume 24 I Number 3