DESIGN: DEAR MR PLUMBER
55
Grey water as part of national
building regulations?
Due to the water situation in South Africa, and even across
the world, the use of grey water has become a top priority.
By Vollie Brink, Pr Eng
At the moment, we do not have a national building
regulation or a code for the use of grey water;
therefore, a new working group of the SABS has
been established to develop such a standard. in a low-cost system, you should not use the grey
water from the kitchen sink and also not from the
dishwashing machine due to the grease and fat
content in the wastewater from these fixtures.
The working group has the option to develop a brand
new South African document or borrow from other
standards and codes and then chop and change to suit
our local situation and conditions. More upmarket systems can treat the wastewater
from these fixtures (even to a potable state), but it is
expensive and probably not affordable for low-income
households. It also requires competent maintenance,
which incurs costs.
Building regulations must also take note of the local
socio-economic, cultural, and technical situation and
therefore, the implementation of a new grey water
code must be carefully designed to suit the needs of
the various communities. Technical, health and safety,
and economic challenges will need to be addressed.
Grey water will require changes to be made to the
drainage and water supply systems. It will have
economic implications and it challenges the matters
of affordability, acceptability, and resistance, putting
pressure on the need for maintenance, which is
generally a fundamental problem in South Africa.
However, we have to use grey water due to the water
situation here and all over the world.
The question remains whether the use of grey water
will become compulsory. It seems it will be; therefore,
we have to change SANS 10400-P to accommodate
a drainage system that will basically be a two-pipe
system from top to bottom, but with the kitchen sink
and the dishwashing machine separate.
The wastewater from the kitchen sink and the
dishwashing machine may be discharged through the
soil water pipe and connected directly to the drain, but
the other (useable) grey water will have to be collected,
treated, and used through separate water supply
piping for the flushing of toilets, or used for irrigation
for certain approved plants. The conditions are to be
formulated in the new SABS document.
THE DRAINAGE SYSTEM
Before 1977, a drainage system consisted of the
so-called two-pipe, fully ventilated system — and that
was it. The two-pipe system comprised two separate
pipe systems, the one for the soil water and another
for the wastewater, but after 1977, the single stack
or one-pipe system was propagated and the anti-
siphonic, or trap ventilation, was basically discarded.
These changes rendered more cost-effective systems
and became the norm of the day. Grey water in general almost always ends up in a lower
position than the fixtures where it comes from, and
then has to be stored and lifted to a higher position to
be used. This normally requires a small pump, which
can be a solar pump that will need a backup for the
evening, unless it is pumped into a high-level tank.
The use of grey water will change the design of the
drainage system back to a two-pipe system where
the soil and wastewater is separated so that the
wastewater can be re-used. It must be noted that We wish the working groups all the best and request
that they expedite this work and give us guidance
to install appropriate, cost-effective, and safe and
sound solutions. PA
www.plumbingafrica.co.za
We are entering exciting times. We must be creative to
survive with less and less water and we have to plan and
execute NOW, and not wait until the problem is upon us.
Vollie Brink
Vollie Brink is one of the
industry’s longest serving
wet service engineers.
He continues to serve on
SABS committees and has
been involved in the
Green Building Council Star
rating system.
Brink continues to consult
for various organisations
while enjoying a well-
earned retirement.
We have to use
grey water due
to the water
situation here
and all over
the world.
May 2018 Volume 24 I Number 3