58 TECHNICAL
Let’ s talk about backflow prevention
With so much attention being focused on the standards and regulations that surround the generation of hot water in a home( think of the recent changes to SANS 10254 and the installation requirements of heat pumps and solar installations), you would be forgiven for letting something like backflow prevention slip your mind.
By Richard Bailie
About the author
Richard Bailie completed his apprenticeship in Kimberley and qualified as a plumber in the early 1990s. In 2000, he opened his own plumbing business, Springtide Plumbers, in Cape Town. He serves on the national executive and technical advisory committee for the PIRB. He is the vice-chairman of IOPSA in the Western Cape and has been auditing projects for the PIRB for approximately six years. He conducts training for IOPSA and the PIRB through webinars and classroom-based platforms, delivered to plumbers, architects, BCOs, and Builders Warehouse staff.
It is, after all, one of those trivial things we have all heard of, and we know it resides somewhere within the standards, but nobody really pays it any mind.
The truth of the matter is that these oft overlooked requirements are vital to any sound plumbing system. May I remind you that backflow prevention as a concept plays a big part in ensuring we all have clean water running from our taps. Without it, our potable water network would be rendered all but useless.
So, when we talk backflow prevention, it means just that: the prevention of a substance( in this case water) from flowing in a direction within a system that is opposite to the intended direction of flow. In essence, we are permitting the water to enter a space and once it has passed a certain point, we deny it a path back.
But why? Well, in all cases where backflow prevention is required, there would be a possibility of contamination. In other words, in these situations, water can come into contact with hazardous substances, for example chemicals or waste, and once mixed with the water, these cannot be allowed to flow backwards to enter the potable supply, and for this purpose there are several technologies we employ. When do you need to install a backflow preventer, and which type must be installed? This is determined by the standards. For installations that do not require a rational design, we refer to SANS 10252-1 and Annexure D of the same.
SANS 10252-1( 7.4) is a section called“ Preservation of Water and Water Quality”, and it has several subsections worth noting. Under“ General”, it tells us that we are to take adequate measures to prevent the deterioration of the quality of water in any water installation, including preventing any substance entering that could adversely affect the potability of the water. It goes on to say that when storing water, we are to ensure that the quality of that water is maintained as well.
The onus is on us, the installers. Remember that when we issue CoCs, we are stating that we as registered professionals have given that particular installation the okay as per the requirements of the various mandatory standards. If you determine that a design has fallen short of the requirements, you should be engaging with the designer to educate them and have it changed.
As is sometimes the case, the standards can be cumbersome to decipher and translate into practical guides, and they tend to jump around due to the way in which they are set out. So, if you want to find out about backflow prevention, you cannot simply go to a section of that name and find everything you need, you need to look up what is written about backflow prevention under the various sections of the standard. In the case of SANS 10252-1, there are five sections after the Scope, Normative References, and Abbreviations— eight in total. They are:
• Section 4: Initial Considerations for Design
• Section 5: Materials, Pipe, Fittings, Components and Fixtures
• Section 6: Layout
• Section 7: Design
• Section 8: Installation
• References to backflow prevention are made in sections 5, 6, 7, and 8.
Subsection 7.4.2 is“ Connections” and it speaks of the general rules surrounding which connections are allowed. So, for example, it prohibits the connection between:
a. a general installation conveying water from the supply main and an installation conveying water from any other source of supply;
September 2018 Volume 24 I Number 7 www. plumbingafrica. co. za