56
TECHNICAL
56
TECHNICAL
What is
backflow and
why must
we guard
against it?
Movement of any substance
in any direction is called flow.
So why the term backflow when water
moves from an installation towards
the municipal potable supply?
By Patrick Gordon
Firstly, it is assumed that the water in any installation
originates from the municipal supply and so the water that
flows back towards there is viewed as flowing back, and thus
called ‘backflow’. In most instances this would be the case, so
why would we need to guard against it? What has happened
to the water that makes it unsafe to return it from where
it comes?
Firstly, we need to take cognisance of the fact that once the water
passes the water meter, it now becomes the responsibility of the
homeowner and the municipality no longer has control over what
happens to it. Once they have lost control over what happens to the
water, they do not want to let it back into the municipal system.
We could let the water back into the municipal system if we had it
tested and certified as SANS 241 quality compliant, but we know that
that is not practical. What could be viewed as potential contaminants?
• We often have water softeners on the supply to the home and this
is done by adding chemicals to the water.
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September 2019 Volume 25 I Number 7