The Southern African Plastic Pipe Manufacturer Association (SAPPMA) is firm that recycled plastic cannot be used in pressure pipes. Pressure pipes are used to transport drinking water, gas, and wastewater when a system cannot rely on gravity. These pipes must be able to withstand pressure for extended periods of time and be reliable in the long term – 50 years or more.

Plastic and its use have been at the centre of sustainability issues, so why is it that recycled plastic is not an answer for these circumstances?

Under pressure

Peter Sejersen, technical manager of The European Plastic Pipes and Fittings Association (TEPPFA), says, “the first issue we run into is that not all plastic for recycling is made equal. It is difficult to control the quality, and cleanliness of this plastic so recycling it would yield a plastic that is not as durable as virgin material.”

TEPPFA is the European equivalent to SAPPMA, and even when relying on Europe’s robust recycling initiatives there is room for error. “Having full control over the quality of plastic used in recycling makes a positive impact — however, recycled plastic still doesn’t match the durability of virgin plastic,” adds Sejersen.

Jan Venter, CEO of SAPPMA, cautions that using recycled plastics in high-density polyethylene (HDPE) pressure pipe violates both international and national standards (ISO/SANS 4427-2). The practise is not only illegal but also poses a significant risk to public health and infrastructure reliability. Despite repeated warnings, the association reports that the use of sub-standard “80/20” pipes – made with 80% virgin material and 20% recycled material – is still prevalent in the local market.

He points out that the relevant HDPE pipe standards only allow for the inclusion of reprocessed material originating from a manufacturer’s own, in-house production scrap. Since no pipe manufacturer generates 20% internal waste, any pipe labelled as 80/20 will, by default, contain external recycled material – making it non-compliant with the national product standards and SAPPMA’s Code of Conduct.

Tests using recycled plastics

Pipes must undergo a pressure test to test their “hoop strength,” and this is where plastic made for this purpose shines. A pilot study in Denmark tried three different 110 mm pressure pipes, one with 25%, one with 60%, and one with 75% recycled materials. All three failed the pressure test. The study then repeated this with a 25% recycled material pressure pipe using pelletised plastic and this did allow the pipe to pass the 1000-hour pressure test, but Sejersen adds, “only barely.” It is important to note that this pipe had a ‘brittle failure’ as opposed to a ‘ductile failure’ once again highlighting that recycled material is not suitable for pressure pipes.

Other pipes with varying degrees of recycled material were tested:

• 315 base, 200 mm connection pipe using 60% recycled material. One connection passed, the other failed the 1000-hour pressure test.
• PE Twin Wall, 315 mm pipe. One with 100% recycled material in the outer layer, and one with 50% in the outer layer. Both production runs failed the 1000-hour pressure test.
• PP 200 mm pipes with 45% recycled material. These failed the 1000-hour pressure test.
• PVC 200mm with 45% recycled material on the middle layer: This passed the pressure tests.

Sejersen stresses that, “Some of the products did pass the pressure test, if only barely, but it is also important to note that recycled material is not suitable for drinking water pipes. Drinking water must be clean and be free from any plastic migration from the pipes. When using recycled materials, you do not know the source and it could be coming from packaging materials from pesticides or other toxic substances. These substances will migrate into drinking water making it unsafe.”

“The use of recycled material from external sources in pressure pipe systems is strictly prohibited for a reason. It drastically compromises the performance and lifespan of the pipe, and when used for potable water, it could have serious health implications. Our industry cannot afford to cut corners for the sake of cost-saving. The long-term risks and financial consequences are simply too high,” Venter warns.

The opportunities of recycled plastic

While not suitable for pressure pipes or drinking water pipes, recycled plastic can be used in non-pressure pipes not used for drinking water. Non-pressure pipes are used for sewers, stormwater, as well as land and building drainage.

“As the world embraces circularity and sustainability, there is a definite use for recycled plastics in non-pressure pipes. Our tests show the theme to be perfectly suited for this job,” says Sejersen, “it is also important to understand why we should look at recycled plastic where possible.”

“The manufacturing of plastic pipes accounts for nearly half of the carbon dioxide of an entire project including installation,” says Sejersen. From this understanding, the use of recycled materials where possible becomes imperative to carbon savings. This is also where the introduction of biobased materials or chemical recycling– a process that transforms plastic to oil– can be used to mitigate the harm of plastics used in pressure pipes. “While non-pressure pipes can benefit from recycled plastics, we must still look into reducing the impact of pressure pipes by means other than traditional recycling.”

In Europe, plastic production is decreasing while in Africa it is increasing. Drawing on Europe as an example, in 2022 they produced 400 Mega Tonnes (MT) of plastic, while recycling 50 MT of plastic in the same year. South Africa produces about 2,5 MT of plastic per year and recycles 430 000 tonnes (0,4) MT. Both places are comparable as Europe recycled 19% of its plastic production, and South Africa recycled 17% of its total production.

This figure shows that there is room to grow, and using recycled plastics in non-pressure pipes is a step forward to reduce South Africa’s carbon impact.

Consequences of using recycled plastic in pressure pipes include:

• A drastically shortened operating life, resulting in unexpected and costly failures.
• Disruption of critical services due to premature pipe bursts or leaks.
• Health risks, especially when used to convey drinking water.
• Legal and reputational risks associated with transgressing standards.