Water, Sewage & Effluent January February 2019 | Page 13

About the author
Vollie Brink (Pr Eng, MSAICE, MPMISA, MFEASA) 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’s Green Star
rating system. Brink continues to consult for various
organisations while enjoying a well-deserved retirement.
It’s all about relevance and applicability. There are only
seven specific regulations relating to performance and
there are more than 30 deem-to-satisfy rules, which are
not relevant to rational design.
By definition, a regulation is compulsory and any
design must comply with it. To the contrary, deem-to-
satisfy rules are merely a recipe for how to comply with
the performance.
For this reason, I propose another element, which
I call ‘principles’. A principle is important, as it is a
guide for good practice and a means of preventing
potential problems.
Principles of rational design
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One of the principles is that, in horizontal situations such
as horizontal branch pipes and horizontal discharge
pipes, the soil and wastewater pipes must be kept
separately. This is critical to prevent raw sewage from
discharging through a shower or bath in the event of
a blockage in a combined horizontal branch pipe or
collector horizontal discharge pipe inside a building and,
more specifically, inside a hospital.
This is a typical example of ‘design-to-prevent
problems’, which is a basic responsibility of an
engineered design by a registered professional engineer
or technologist.
A European factory representative once challenged
me by saying, “It is not the duty of the engineer to design
to prevent problems.” This is the most irresponsible
statement I have ever heard from a technical person.
The EU design standard allows soil and waste fixtures
to be connected on the same horizontal branch pipe, but
this is not allowed by SANS10400-P — in any system.
Regulation states that in the case of a ‘group’, all
the fixtures of a house, flat, or apartment shall be
‘separately connected’ one by one to a combined stack
pipe or to the waste stack or soil stack in the case of the
two-pipe system.
In the case of a ‘range’, each range shall be connected
separately to the combined stack pipe or otherwise to the
two-pipe system separately to the soil or waste stack.
The reason behind these deem-to-satisfy rules is to
keep soil and wastewater separate in the horizontal
position and to prevent raw sewage discharge from the
lowest-situated fixtures such as the shower and bath,
and thereby prevent a health risk.
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