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DESIGN: DEAR MR PLUMBER
Water conservation and
drainage blockages
It is wonderful to see how much effort is going into water
conservation. But water conservation should have been a top
priority years ago, so why is it that all these so-called experts are
only voicing their brilliant ideas after the fact?
By Vollie Brink, Pr Eng
Nowadays, even the newspapers are brimming with
advice on how to use less water. A new standard is being
developed on water conservation, even though we could
not develop water regulations since 1977.
I was once asked to give a talk about civil engineering at a
technical high school to give the pupils an idea of this kind
of work, while other engineers had to talk about the pros and
cons of all the other engineering careers.
I was the last speaker, which I was happy about because then I
could say what I wanted to and nobody could repudiate me. I told
the audience that we can forego all the other engineers and still
survive, but we cannot do without the civil engineer and water.
You, Mr Plumber and Mr Engineer, play a crucial role in
keeping our people alive.
For many years we have accepted water as a fait accompli
and that it is plentifull. And then suddenly, the situation in
Cape Town happened. This situation has opened many eyes,
and many water engineers have predicted what we now have
seen play out.
We have heard and read a lot about the water problems in the
old mines around Johannesburg and how it is going to affect
us all, and that places like Gold Reef City are going to be
swamped — and then everything just went quiet.
Water engineering needs long-term highly skilled engineering
planning and highly skilled budget planning to go with it. It
also needs highly skilled engineers to design and manage the
construction and highly skilled human resources to do the work.
I asked such a ‘highly skilled engineer’ why the forward
planning was not done, and his answer was that it had been
done, but not implemented. You can have wonderful planning
but if it is not implemented, then it is not worth the paper it is
written on and remains a pipe dream.
July 2018 Volume 24 I Number 5
I attended a world conference in 1980 in Berlin, and I was
invited to see the research that had been done by Professor
Knaublaag of the Technical University of Berlin. The professor
was doing research on flushing systems to see by how
much he could reduce the water and still have an acceptable
flushing of the effluent through the piping.
He had systems set up with glass piping and cameras
down the piping to see what happens when the system is
flushed with various flushes. He produced solids from a
certain substance and texture to represent human solids
and flushed it through the WC and configuration of piping to
see to what extent he could reduce the flush water. In those
days, we wondered why he was working on something so
‘unnecessary’, but he was a visionary and knew that water
would become a problem.
Some European manufacturers have started making WCs that
use less water, and most have reached the point where their
system has two flushes: one for urine to flush with three litres
and another for flushing solids with six litres; this seems to
have become the norm.
Talks and efforts on how to minimise the flow rates of fixtures,
such as the WC and shower and the various taps, have
surfaced again. Most of these people see the solids and paper
disappear from the WC pan, but they do not see what happens
downstream from the WC, inside the drainage piping.
You need enough water and air inside the piping, and the piping
must be at a specific minimum gradient to transport the effluent
otherwise it will cause problems, which we call blockages.
Blockages are serious health risks, and two of the key
elements of the National Building Regulations are to protect
health and to ensure safety. The gradient of a drain or sewer
pipe (note: there is a difference between the definition of a
drain and a sewer) is critical to transport soil and waste from
the various fixtures.
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