Piping design part 1: which pipe for what purpose?


By: Fiona Ingham.

Choosing the right materials calls for an objective understanding of the conditions, strengths and weaknesses of each material.

Which are the best materials? Which last longer and perform better? Every professional naturally has their own favourites based on their experience and how they have been influenced by the experiences of others. Some types that have been used for decades, have fallen out of favour as newer, better materials have become available.

Plumbing Africa asks the experts themselves to discuss both the advantages and the disadvantages of copper and HDPE as materials for the conveyancing of water and waste in the plumbing industry.

“The main advantages of copper pipes are that they are antimicrobial and prevent pathogens from growing inside the pipe. The major disadvantage is well known in South Africa: copper is prone to being stolen,” says Evert Swanepoel, centre director of the Copper Development Association South Africa.
Copper’s antimicrobial properties are vast. The first known medical use of copper is found in the Smith Papyrus, an ancient medical text written between 2600 BCE and 2200 BCE. Copper pipes are thought to be safe, are fire resistant, and its small internal diameter lets it fit into smaller, tighter places than flexible piping.
Swanepoel says copper is used in all plumbing, refrigeration and heat exchange applications, above or below ground. The most common installation mistake made is to use either too much or the wrong flux, which finds its way to the inside of the pipe and can lead to pitting. There is also a tendency to use worn tooling to bend copper pipes, which results in damage and poor quality of the bend.

Although it is easy to work with and produces cleaner water than other tubing, the greatest disadvantage is unfortunately that it is not the cheapest material to use in piping. In addition, “cheap imported copper water tubing not made to the correct standard often does not perform properly, which then gives it an unwarranted negative reputation,” he says. Unfortunately they also creak and shudder with the familiar ‘water hammer’ noise, as homeowners with copper water tubing can attest to. Water acidity can also present problems for copper.
“Copper is completely recyclable and environmentally friendly. There are various SABS specifications for copper tubes and fittings which ensure quality and accuracy of fittings. If you purchase an SABS certified copper tube in Cape Town and buy the SABS fittings in Johannesburg, it will fit,” Swanepoel says.
But a skilled and experienced plumber will use a mix of materials, such as copper for the main lines and then Pex and CPVC for branching lines, identifying the best material for each job. Whereas copper is not developing as a material, the field of plastic is changing daily as advancements are made. Plastic does not transfer heat and is more energy efficient. In sanitary sewer pipe applications, PVC accounts for 75% of all installations in the US.

“The main advantages of copper pipes are that they are antimicrobial and prevent pathogens from growing inside the pipe.”


High-density polyethylene (HDPE)
According to Pluvia consultant Izaan Nel at Geberit, HDPE is much more durable and flexible compared to the other materials available in the market. It’s lighter, faster to install and much more convenient to use.
“The expansion of any pipe is regarded as a disadvantage in the industry. We design and ensure that the movement is accommodated for by the use of expansion sockets in all the right places. Joining HDPE to any other material can also be quite disadvantageous due to additional items needed to do this; furthermore, the possibility of leaks is far greater as different pipe materials have different characteristics and joining them together is not the right solution. When one mixes the installation with different products, the chance of the product warranty falling away is high.
“HDPE can be used almost anywhere. It’s installed in one of the highest mountain ranges – the Swiss Alps – and as low as below sea level,” says Nel.
The main uses of HDPE are for sewer reticulation and for the Pluvia syphonic rainwater system. It can also be used as sleeves, for air-conditioning system overflows, cast in concrete, exposed outside a building and underground.
“HDPE uses extend to applications both above ground and below ground. Joining of the pipes is the most common problem for all pipe reticulation we face. The lack of installation of the expansion sockets is a big issue, as this is a mandatory requirement for any HDPE exposed pipe run. It’s used to allow for the movement of pipe, except for soil and in concrete installations,” she says.
Another common mistake concerns the fastening of the HDPE runs. Installers tend to either forget installing them at the anchor points altogether, or they do not fit the required amount of brackets to support the pipe run. The installation mistakes always come down to a lack of product knowledge and not having the right tools available. Finally, Nel says HDPE is competitively priced against other similar products.

Aadiel Woods, who has been with Geberit for more than 20 years, had the following to say: “We built an outdoor shower system out of HDPE on top of a bakkie for the owner to go camping and travelling in Africa. The system also doubled up as a roof rack. The black HDPE piping retained the heat and provided continuous hot water for the campers’ showers. The success of this project encouraged one of the original campers to use the same system to heat their swimming pool. This was a special project as it identified that there are many alternate uses for HDPE.”
Plumbing Africa will look at the advantages and disadvantages of galvanised steel and cast iron in the next edition.

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