TECHNICAL
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An RPZ valve.
I wouldn’t mention this fact except to illustrate the importance of
backflow prevention and its ongoing operation. You do not see
this insistence for a maintenance regime in the geyser installation
standards, for example. It is recommended, but not enforced to
the point where you are prohibited from installing one for lack of a
maintenance regime.
Now, lets revisit the various mentions of backflow prevention in
SANS 10252-1. Remember how the different sections in the
standard are organised? 6 for layout, 7 for design, and so on?
It would then stand to reason that each reference to backflow
prevention in these sections are done so within a certain context,
so for example:
5.4.15 (materials and the like) says that check valve shall comply
with SANS 1808-10, and that swing-type metal-to-metal check
valves shall not be used in potable systems in buildings.
6.3 (layout) gives various minimum and maximum distances between
components, configurations, and other positional requirements.
7.4.3 (design) appears earlier in this article and speaks to when
and where backflow preventers should be used.
8.4.2 (installation) lists the following installation requirements,
which I think are worth listing here:
a. that it can be inspected;
b. that a condition of backflow can be detected;
c. that it is readily accessible without having to alter the
surrounding structures;
d. that it cannot be flooded by any liquid; and
e. that vacuum breakers are installed on anti-syphon loops.
We can see the importance the creators of the standards
place on backflow prevention. Local authorities are usually
very strict on this as well, considering the legal ramifications
for them when it is shown that they were unable to guarantee
the potable water quality provided, as is their mandated duty.
It boggles my mind therefore that we as plumbers do not pay
more attention to this. I am just as guilty of this, some thing I
aim to change going forward. PA
September 2018 Volume 24 I Number 7