WATER
From page 13
tion:
K A five-minute shower
using a reasonably conservative shower head will
generate about 35 litres. This
can be considerably reduced
using a modern water-saving
head.
K A standard bathroom basin
holds eight litres if filled
below the overflow hole.
K A standard kitchen sink
holds 15 litres if not filled to
the brim.
K Modern water-efficient
dishwashers use as little as 15
litres per cycle.
K Your washing machine, if a
modern machine, uses
between 50 and 120 litres
per load and if an older type,
about 100 to 170 litres per
cycle.
K If you still use a bath for
your daily hygiene, bank on
using 300 or more litres per
tub, depending on how full
you make it.
Q Water used for mopping
and scrubbing floors can be
A family of three, with modern appliances,
should generate just more than a drum-full
of grey water a day
added, at a rate of eight to
ten litres per bucket, assuming the used contents are
emptied into the drain rather
than flung out into the
garden. Similarly, a few litres
can be added for the water
used to rinse basins, showers
etc.
Thus, a household of three
people, showering, using a
dishwasher in the kitchen and
a washing machine once daily
each, can work on about 250
litres of grey water generated
daily, assuming they use half a
basin each a day, twice, for
brushing teeth, shaving etc,
and two full kitchen sinks
daily for washing pots and
pans, rinsing vegetables etc.
Remember this is not the
household's TOTAL water
usage. One needs to add
water consumed (eg drinking
water, tea and coffee) as well
as toilet flushing (at least eight
litres per flush in a standard
cistern with reduced capacity
either through the addition of
bricks or through adjustment
of the ball valve).
Taking this calculation further,
250 litres of water applied in
the garden as rain would be
the equivalent of a good
soaking (10mm) of rainfall
2
over 25m , or an area
measuring 5m x 5m.
But for you to use even this
quantity safely over the long
term it should be filtered,
firstly to remove solids (food
scraps, hair, soil residue from
vegetable washing etc), but
also to deodorise it and
remove fats, oils and greases
which, in time, will clog your
soil.
It is also advisable to partly
sterilise the fluid by exposing
it to the ultra violet rays of the
15
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sun.
The fact that the remaining
fluid is high in soap and
shampoo residue is not of
undue concern as these
compounds are largely made
up of phosphates and
nitrates, which are chemical
fertilizers and are therefore
beneficial to plants.
More importantly, if you use
grey water for irrigation, is to
keep a watch on the pH of
your soil and adjust if
necessary. Better still, rotate
Continued on page 17