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PRESS RELEASE
PVC touted as the material of choice for large stormwater drains, sewers
6 December, 2016: The recent introduction of 560 mm and 630 mm polyvinylchloride (PVC)
sewer pipe is challenging the dominance of concrete as the material of choice in this market
segment, according to DPI Plastics Technical and Product Manager Renier Snyman.
While PVC constitutes 95% of the total sewer-pipe market in the US, it is only predominant in small
to medium pipe sizes in South Africa. However, the myriad advantages of PVC over traditional
materials such as concrete means it is ideal for stormwater drains and large sewers.
Like most thermoplastics, PVC has a smooth surface, which translates into low friction or resistance.
“This presents quite an advantage for pressure pipes and gravity sewers,” Snyman comments. PVC is
also classed as a semi-flexible material, meaning it has good resistance to ground movement.
Traditional materials such as clay and concrete, on the other hand, have high stiffness and are hard.
“The moment there is a little bit of movement, they can crack and spring a leak. This poses a major
health risk with sewer-pipe systems in particular,” Snyman stresses. Another benefit is that PVC can
be painted easily with either an exterior acrylic or alkyd enamel paint.
“In South Africa, it is quite popular to paint soil and vent pipes, as we tend to plumb on the outside
of a wall, and these external areas are highly visible as a result,” Snyman adds. In addition, PVC has a
high resistance to damage and scratches, which means that sewer lines made from this material can
be rodded or cleaned by means of water-jetting.
The smooth internal bore is not only non-corrosive, but also resists algae and scale build-up. This
may not seem to be an issue affecting plastic pipes, but Snyman explains that a biofilm does form
inevitably, which affects the flow and volume. However, this is negligible compared to other
materials such as concrete.
“The end result is a pipe that still performs reasonably well, compared to a new pipe. That is quite
important, especially as any pipeline is a long-term investment, with an average lifespan of 50 to 100
years,” Snyman points out. PVC also has double the tensile strength of high-density polyethylene
(HDPE), meaning a thinner wall thickness. This not only reduces costs, but means that PVC has a
lower carbon footprint as it uses less raw materials.
“A major advantage of PVC for sewer pipes is it has a high modulus of stiffness. A sewer pipe is
empty for most of its lifespan, with only the ground pressure bearing down upon it. Trenching plays
a role here, but the pipe has to have a certain stiffness in order to maintain its round shape. “If a
sewer pipe deforms excessively or collapses, it can result in blockages in the line. Hence it is
important that the pipe retains its circular shape, and here PVC plays a critical role,” Snyman
elaborates.
Extra benefits include the fact that PVC is formulated specifically to be highly UV-resistant, as well as
having excellent fire properties. The high Limiting Oxygen Index (LOI) means it is difficult to ignite. In
addition to normal rubber ring joints, solvent welding can be used to join PVC pipes, which is easyto-use and cost-effective. The normal temperature range of a sewer and drainage system fluctuates
from zero to 60°C. “PVC performs well within that range,” Snyman asserts. It also has a low coefficient of linear expansion, about half that of polyolefins.
PVC came under the spotlight at the Southern African Plastic Pipe Manufacturers’ Association
(SAPPMA) Pipes X conference, held at the Byte Conference Centre in Midrand on 6 September,
where Snyman gave a presentation on the potential of this material for large-diameter sewer pipes.
Ends
Notes to the editor
To download hi-res images for this release, please visit http://media.ngage.co.za and click the DPI
Plastics link to view the company’s press office.
About DPI Plastics
DPI Plastics is a leading manufacturer of PVC and HDPE water reticulation and drainage pipe and
fitting systems, with two ISO 9001 certified South African factories, one in Johannesburg and the
other in Cape Town. In addition, the DPI Group has wholly-owned subsidiary plants in Namibia and
Botswana and joint venture manufacturing operations in Mauritius, Tanzania and Angola, producing
plastic pipes to the relevant SABS or international specifications.
DPI Plastics Contact
Martine Goodchild
DPI Plastics Marketing Manager
Phone: (021) 957 5600
Fax: 086 505 6484
Email: [email protected]
Web: www.dpiplastics.co.za
Media Contact
Renay Tandy
NGAGE Public Relations
Phone: (011) 867-7763
Fax: 086 512 3352
Cell: 082 562 5088
Email: [email protected]
Web: www.ngage.co.za
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