FEATURES
48
A typical drainage installation for a public restroom.
An HDPE drainage installation in a commercial building.
WHY IS THE QUALITY OF MATERIALS IMPORTANT?
The basis of the NBR is health and safety, and quality
directly relates to health and safety. It also relates
to longevity (lifespan and durability) and it relates to
operation, maintenance, and costs.
Inferior quality of materials can be dangerous and
require more costly maintenance and may be a health
threat. Low-quality piping has caused serious technical
problems, costly replacements, and expansive water
wastage. The SABS standards for materials and many
other international standards are for good quality, safe,
and economic installations.
When it comes to the installation and management of
drainage, it is crucial to consider not only the obvious
health risks, but when using products of a lower quality
that do not last, the risk of human contact becomes
greater, which leads to greater probability of health
issues. This includes the risk of leaks contaminating
potable water supply or boreholes, which not only affects
a single point but can harm entire communities.
Better quality, or best quality, is important for a
long-lasting system. The general lifespan of a
commercial building is between 20 and 25 years and
the quality of piping, fixtures, and equipment must
be able to last for this period. Updated standard
development requires piping to last as long as 50 years.
May 2019 Volume 25 I Number 3
WHAT IS THE CORRECT PREPARATION FOR PIPE
BEDDINGS AND COMPACTION?
SANS1200 contains the necessary information on this
topic. There are a number of important elements, such
as the following:
• The ‘excavation’: The trench must not be over-
excavated, deeper than the invert levels, and then
backfilled with soil with no compaction.
• The bottom of the trench must be the same density
as the adjoining material and not be able to subside
when water penetrates the trench later on, causing
the pipe to subside, and therefore resulting in not
being straight — which causes blockages.
• If necessary, the bottom of the trench must be
compacted.
• The bedding of the piping is clearly specified in the
standard and other pipe manufacturers’ manuals.
However, the best pipe bedding is river sand and
normally at least 100mm thick under the barrel of
the pipe and around to the middle of the pipe.
• Once the pipe is pressure tested, then the pipe
is covered with river sand (in the absence of river
sand, a granular material free from stone can be
used as specified in the standard) to 300mm above
the top of the pipe. This cover of 300mm over the
pipe can be lightly compacted.
• Once the pipe is covered with the 300mm thick
cover, then the rest of the backfilling can take
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