Water, Sewage & Effluent January February 2019 | Page 15

It is crucial to use the best and most robust
drainage piping for heavy-duty high-
maintenance drainage. Most of all, it must
have excellent watertight and airtight
joints that cannot pull apart with time.
Sanitary drainage piping quality
Before, we used cast iron above
ground and clay pipes below ground,
but this has changed to other materials:
robust pipe material such as HDPE with
welded joints is now used both below
and above ground. What is important
is that the pipe material must be robust
with permanent leak-free connections
for both above and below ground.
The bottom line is, competent
services design engineers are
essential to best-practice systems
design. The proposed definition of a
competent services design engineer
is a registered professional engineer
or registered professional technologist
with proven specialist experience in the
design of hospital services, under the
mentorship of a specialist Pr Eng or Pr
Tech Eng with a minimum of five years’
experience. Anyone less qualified
than that is not competent to deal with
rational design. 
contaminated air from entering
passages where medical staff, patients,
and visitors walk.
Hospitals now have hand-washing
facilities at frequent intervals, but
there is a gap between the sanitary
drainage system and the sterile
spaces in the hospitals.
It is important not to have long
horizontal drainage piping in ceilings,
as this does not allow for the minimum
gradient of 1 in 60 inside the building
and clashes with all the other services.
Any horizontal drainage in hospitals
should not be longer than 6m and
should drop down in stack pipes.
Kitchens should be fitted with floor drains with suitable metal grids and a channel to
discharge into a water trap, designed in a way that permanently isolates the kitchen
area from the sanitary drainage system.
innovations
ventilation), as it ventilated directly
from the back of the trap.
Air and hot water always rise, which
is why ventilation pipes are always
vertical.
In modern systems that do not
have trap ventilation or anti-syphonic
pipes, the air in the effluent from the
fixture is first forced downwards
and horizontally, up to the stack pipe
connection, and then the air escapes
upwards through the ventilation pipe
and out into the atmosphere.
The ‘old’ system was better in that
the air went directly up through the
anti-syphonic pipes and out to the
atmosphere, and therefore carried
the foul, contaminated air out of the
building.
I believe that the full trap-vent system
is a solution for the contamination
problem in hospitals. These ventilation
pipes must also be fitted with a positive
electro-mechanical air extraction
device so that when the plumber
opens a pipe, foul, contaminated air
cannot escape into the room where
the piping is situated.
A competent hospital services
design engineer should be able to
design a system in such a way that
when the pipes are serviced, the foul
air cannot contaminate the hospital
environment. However, the architect
also plays a major role in designing
the building to cater for service areas
such as ducts and creating spaces
where the hospital environment
cannot be polluted.
The trend with new hospitals is to
minimise on space required for ducts
and even plant rooms to save on costs.
The ‘old’ hospitals had ‘dirty’ corridors
and spaces where the ‘dirty’ services
were conducted, which allowed for
maintenance and services without
entering sterile areas. Perhaps we need
to relook at how this was done?
The design and position of the sluice
room should also be considered and
provided with an exhaust system
for sanitary drainage to prevent
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Water Sewage & Effluent January/February 2019
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