A new building sanitary
drainage system: Part 1
DESIGN: DEAR MR PLUMBER
25
By
Vollie Brink
The SA National Building Regulations which were promulgated in
the 1970s contained a section for the design and construction of
the sanitary drainage of buildings, which were called SABS 0400-P,
and later became SANS10400-P. This is Part 1 of a two-part article.
The abovementioned building regulations were
relevant and applicable for private owned housing and
offices and contained regulations and rules for the
design and construction of sanitary drainage for these
types of buildings.
These systems or pipe configurations had nothing on
buildings such as hospitals, shopping centres, industrial
buildings, drainage on Dolomite and other special buildings
such as jails or police stations.
The reason for this was basically because these buildings
were mostly government-owned buildings, and the various
government departments and parastatals had their own
building regulations and were not required to have their
building plans approved by the local building control bodies.
Until to-date (2020), the SANS10400-P does not have
anything specific for hospitals and all the other buildings as
mentioned above and therefore it can only be designed as a
rational design.
This Standard, SANS10400 -P, described a number of
systems with the following names:
• Two pipe system, which is basically a system with
two stack pipes, one for the soil water and another
one for the wastewater with branches connected
to the separate stack pipes and fully ventilated by
means of a trap ventilation at each fixture. This used
to be called ‘antisyphonic’ pipes and it made the
system very expensive due to all the extra piping.
These antisyphonic ventilation pipes had to be
combined and connected together to a common
ventilation stack pipe.
• One pipe system, which is basically the same as the
two pipe system but consists of only one combined
stack for soil and waste water with or without trap
ventilation depending on the length of the branch
pipes. The so called ‘single stack pipe’ system is
the most modern and does not require antisyphonic
pipes under certain conditions and with certain pipe
connections to the stack pipe.
The question was asked, “why do we have different types
of systems?” and for housing and offices only? Why don’t
we just have a generic drainage system with various
configurations to suit the hydraulic operation of the system
and to suit all types of buildings?
Elements of a system
A system, depending on the height of the building, consists
of the following elements:
Externally from the building to the sewer connection:
• Gully
• Wastewater pipes
• Soil-water pipes
• Stub-stack
• Ventilation
• Drain
• Cleaning eye/ rodding eye
• Inspection chamber
• Manhole
• Sewer connection
Internally
• Stack pipe for combined wastewater and soil water
• Stack pipe for wastewater only
• Stack pipe for soil water only
• Wastewater branch pipes
• Soil water branch pipes
• Ventilation pipe
• Trap ventilation
• Back ventilation
• Ventilation valves
• Horizontal pipes to collect the stack pipes and
discharge it to the external drain,
All these make up the elements of a total system and is
called a ‘drainage system’. These elements can be put
together in any required configuration as a total system to
suit the design and type of any building.
Part 2 of this article will look at the number of principles
which are critically important to a drainage system. PA
Vollie Brink is one of the
industry’s longest-serving
wet services 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 wellearned
retirement.
September 2020 Volume 26 I Number 07
www.plumbingafrica.co.za