Frequently asked questions about PVC pipes

What are the environmental issues for PVC?

PVC is arguably one of the most scrutinised materials in the world. In a study done by the CSIRO in 2001⁽¹⁾ which discussed some of the scientific issues surrounding the use of PVC the following quote largely sums up the history of this situation:

"As with many controversial subjects, there exist conflicting results and differing interpretations of the same data with regard to the issues relating to PVC. Dean (1995) summarises the situation precisely when he states a large number of the perceived risks from e.g. PVC, dioxins, incineration, furnace ash, waste fuel oil, etc are derived from assumptions that have been unsupported or refuted by later studies, but which remain strongly in the public mind".

Some green groups have questioned the environmental performance of PVC with reference to a range of issues relating to:

• chlorine and vinyl chloride monomer (VCM)
• dioxin - created during manufacture and incineration
• recyclability
• use of hazardous chemicals such as heavy metals and plasticisers.

(Note: each of these issues is dealt with individually and in detail later in this section on frequently asked questions.)

"The focus of this debate was initially concerned with the manufacture of PVC but has now shifted to the use and disposal of the material" ⁽¹⁾. This shift is likely due to the resolution of the manufacturing issues that were largely OH&S in nature.

In 1998 and 2001, the CSIRO extensively reviewed recent scientific literature on PVC and concluded: "the balance of available evidence indicates that PVC in its building and construction applications has no more effect on the environment than its alternatives".

In 2004 the US Green Building Council PVC Task Group issued a draft report on PVC related materials. This draft report was based on an analysis of over 2400 scientific papers, submissions from green groups, the building industry and PVC industries. The report concludes "the available evidence does not support a conclusion that PVC is consistently worse than alternative materials on a life cycle environmental and health basis".

Furthermore in 2004 the European Parliament commissioned a Life Cycle Analysis (LCA) study on PVC - "Life Cycle Assessment of PVC & of Competing Materials". This report found no evidence to support a bias against PVC and as a result has placed no restrictions on its use.

⁽¹⁾ "A discussion of some of the scientific issues concerning the use of PVC", Dr P Coghlan, CSIRO, 2001

How is Chlorine and Vinyl Chloride Monomer (VCM) manufactured?

PVC production is a major user of chlorine, consuming around 35% of the manufactured chlorine in the world. Chlorine is used in many products we rely on - medicines, water disinfection, paper and paints to name a few. Chlorine plays a key role in many chemical processes. Whilst there are many naturally occurring compounds containing chlorine it does not naturally exist in its pure state. The manufacture of chlorine involves the breaking down of common salt by electrolysis into chlorine and caustic soda (used in other industrial processes such as aluminium refining).

Chlorine is reacted with Ethylene to form VCM which is then polymerised to form PVC.

Should I be concerned about VCM?

Consumers are not at risk from exposure to VCM. VCM is only present in the polymer raw material stage.

VCM is known to cause a rare form of liver cancer after prolonged high level exposure. The only known deaths as a consequence of contact with VCM have occurred to people involved in the manufacture of PVC. As a result appropriate OH&S procedures have been in place since the mid 1970’s dictating the methods of safe handling of this material. In addition appropriate safe working exposures are in place and manufacturing sites are constantly monitored to ensure a safe working environment is maintained. VCM is very well controlled in the workplace. Confirming the success of this control there have been no known cases of this rare cancer found in workers who have entered the industry since the mid 1970’s.

Is PVC a significant source of dioxin?

PVC pipe contains no dioxin.

The principal sources of dioxin in the western world are municipal and medical waste incinerators - particularly older facilities. In Australia the incinerators are few in number and relatively new and have been engineered to produce very little dioxin. An investigation for Environment Australia in 1998 found that 60-80% of dioxin emissions to air in Australia arise from agricultural burning off, residential wood combustion and bushfires. Waste incinerators and halogen chemical manufacture (including chlorine and PVC production), together contribute less than 1% to the total. This report is available on-line at http://www.ea.gov.au/industry/chemicals/dioxins/pubs/dioxins.pdf. Other more significant dioxin sources include the combustion of coal, ferrous and non ferrous metal manufacture and internal combustion engines.

The level of dioxins in the global environment peaked in the late 1960s and early 1970s. Japanese Government data shows that daily human intake of dioxins fell by 75 per cent between 1977 and 1998 ⁽²⁾. The US EPA has reported that dioxin emissions in the US fell by 80 per cent between 1987 and 1995 ⁽³⁾.

This significant reduction in dioxin emissions is in stark contrast to PVC production that has trebled over the past 20 years - highlighting that the production, use and disposal of PVC has no direct link to dioxin production.

The Swedish EPA found that "a reduction in the PVC content of waste will not change the amount of dioxin emissions in flue gases, or significantly reduce the dioxin content in residual products from flue-gas treatment plants."⁽⁴⁾.

⁽²⁾ Ministerial Council on Dioxin Policy, (1999) Dioxins, Japan.
⁽³⁾ US EPA, (September 2000) Draft Exposure and Human Health Reassessment of 2, 3, 7, 8-Tetrachlorodibenzo-p-Dioxin ... (etc).
⁽⁴⁾ Swedish EPA (June 1996) Report on Disposal PVC Waste.

Is PVC pipe recycled?

PVC pipe is recyclable, contrary to some reports. Both post industrial waste and post consumer waste is recycled.

PVC is a thermoplastic material and as such is readily recycled. Being thermoplastic any waste generated in the manufacturing process is recycled - usually like for like.

PVC pipe is such a durable material that the opportunities for large volumes of material to recycle simply do not exist. When they are available they can be recycled. PIPA, in association with Collex, has successfully established a process to recover plastics pipes from construction and demolition waste across Sydney. Details of this event are found under Plastics Pipe Recycling Trial - End of Trial Report. The process removes practically all plastics pipes from the waste and produces granulated materials suitable for new pipe feedstock. However, it must be recognised that the overall volumes are low for the reasons previously stated.

PVC pipe waste, both factory rework and externally sourced e.g. building site off cuts or demolition waste, is converted into solid wall stormwater pipe, or as a foam or solid core in the middle of multilayer pipe, used for sewer pipe and under ground conduits.

Does PVC pipe contain hazardous chemicals?

The concerns about hazardous chemicals in PVC centre on the use of heavy metal stabilisers (typically Cadmium and Lead) and plasticisers in flexible PVC products (such as phthalates). There are many reports that question the level of concern with respect to these chemicals in PVC. Organisations such as the Vinyl Council have extensive reviews of the scientific papers relating to these chemicals (www.vinyl.org.au).

In the case of PVC pipe the issues can be simplified:

• PVC pipe produced in Australia contains no plasticisers.
• PVC pipe produced in Australia contains no cadmium.
• Lead stabilisers are not used in the manufacture of pressure water pipe in Australia and they are being phased out in other piping applications under the PVC industry's Product Stewardship Program. In any case the impact of lead stabilisers is regarded as insignificant. Small quantities of lead based compounds are used as a thermal stabiliser in some pipe products. The lead stabilisers are held within the PVC matrix and to quote the CSIRO Report from 2001 "the concerns relating to extraction are overstated". In terms of release of lead from PVC pipe there have been extensive studies both in Australia and Europe on leachate from waste water pipes and landfill situations. In both cases the conclusion is that the amount of lead released is insignificant.

How does the Embodied Energy of PVC pipes compare to metal pipes?

Embodied energy analysis quantifies the amount of energy used to manufacture a product. This involves the assessment of the overall expenditure of energy required to extract the raw material and manufacture it into a product. In terms of Embodied Energy PVC pipe products perform significantly better than competitive metallic pipe systems (based on independent CSIRO research ⁽⁵⁾). This advantage is often more than a factor of 2 in favour of PVC products - particularly the PVC-O pipe products.

Read a summary of the report at Plastics Pipe Systems Good for the Environment or study the full report by downloading it in PDF format (227 Kb) Piping Systems Embodied Energy Analysis.

⁽⁵⁾ M.D Ambrose, D.D Salomonsson, S. Burn, "Piping Systems Embodied Energy Analysis" CSIRO 2002.

What is meant by series 1 and series 2 sizes for PVC pipe?

PVC pipe manufactured to AS 1477 is available in 2 size ranges referred to as Series 1 and Series 2. Series 1sizes are compatible with the ISO 161-1 and 161-2 standard size ranges. The Series 2 pipe is compatible with Australian cast iron sizes (AS2280) - this size range is unique to Australia.

For the same nominal diameter (DN) the Series 2 pipes are slightly larger in diameter. Examples of Series 1 and Series 2 outside diameters are given in the following table:

It is important to appreciate that the larger OD of Series 2 translates to a larger ID and hence will influence the hydraulic performance of the pipeline for the same DN value.

What is Oriented PVC?

Oriented PVC or PVC-O is the latest advance in PVC pipe manufacture. By orienting the randomly arranged long chain polymer molecules significant improvements can be achieved in the mechanical properties of PVC. Orientation is achieved by controlled stretching and expansion of the PVC pipe. The result is a pipe with around twice the tensile strength as PVC-U with significantly better fatigue resistance, impact resistance and resistance to crack propagation.

These improvements in mechanical properties allow the pipe wall to be thinner producing a larger bore for the same nominal diameter and pressure class. Therefore for the same DN over 10% improvement in hydraulic performance will be achieved compared to PVC-M pipe and even more so compared to PVC-U pipe.

What is modified PVC?

Modified PVC or PVC-M is a PVC alloy. The addition of modifying agents increases the ductility while virtually retaining the same material strength.

The modifying agents significantly improve toughness and impact properties with resistance to crack growth a key performance requirement. The change in material matrix results in more ductile behaviour and thus enables the factor of safety to be lower than PVC-U. The result is a pipe with a thinner wall and larger bore for the same DN and PN rating offering improved hydraulic efficiency over PVC-U.

Frequently asked questions about Polyolefin pipes

Can you recycle PE pipe?

Yes. PE is a thermoplastic and is readily recycled. Being thermoplastic any waste generated in the manufacturing process is recycled. PIPA, in association with Collex, has successfully established a process to recover plastics pipes from construction and demolition waste across Sydney. Details of this event are found under Plastics Pipe Recycling Trial - End of Trial Report. The process removes practically all plastics pipes from the waste and produces granulated materials suitable for other new pipe feedstock.

What are the common polyolefin materials used in pipe systems?

The most common polyolefin used for pipe manufacture is Polyethylene (PE) but you will find Polybutylene (PB- mainly in small diameter hot and cold water applications), Cross-linked Polyethylene (PEX) and Polypropylene (PP) in other common piping applications.

Frequently asked questions relating to flexible pipe

Flexible pipe systems are recognised as genuinely competitive in both pressure and non pressure applications – a measure of the success of these systems is that they have attracted such a vigorous and targeted campaign from some suppliers of rigid pipe. The following information corrects some of the errors and misinformation being distributed about flexible pipe and provides a more accurate and balanced representation of the facts.

1. Installation Methods

A concrete pipe industry publication states that "failure to install flexible pipes in accordance with AS/NZS 2566.2 would compromise structural integrity and increase the risk of pipeline failure" whilst for concrete pipes the "inherent structural strength of the pipes carries imposed earth and traffic loads" implying that concrete pipe is not installation sensitive.

This implication that concrete pipe is not installation sensitive is incorrect.

One does not need to look far for technical papers detailing cracking of concrete pipe due to poor installation practice. Such a paper is "Cracking of stormwater pipes and the significance of construction loads" by Demartini, Hansen and Lee from Brisbane City Council ⁽¹⁾. In an audit of concrete pipe drainage projects in the mid to late 90’s "some degree of cracking was found in all pipe sizes less than 900mm diameter". They concluded the cracking "was likely related to trench backfilling and compaction methods".

Photos of typical cracking taken from the 94/95 and 97 Brisbane City Council Audits (1)

Similarly in the US there are countless examples of cracked and poor performing concrete pipe. These examples are from Fairfield County and Defiance County, both located in Ohio (photos courtesy of ADS Environmental, Inc)

Preparing proper bedding and side support is crucial for all pipe systems – rigid or flexible. This is particularly so in the case of installations under roadways where the same attention to compaction is required regardless of pipe type if one is to avoid trench subsidence.

PIPA advocates correct installation procedures should be followed for flexible plastics pipe systems and clearly rigid concrete pipes are susceptible to damage from poor installation practices.

2. Why are there different types of plastics pipe and can they be recycled?

The concrete pipe industry nominates the variety of materials and the fact that they can be recycled as negatives for plastics pipes. Quite the contrary is true - this versatility in materials selection and the ability to recycle "cradle to cradle" are enormous positives for plastics pipe. Having only one material option is limiting.

The variety of plastic materials coupled with the versatility of different manufacturing options allows plastics pipe systems to be tailored to the needs of the project using material efficient products that are environmentally responsible. Thermoplastic materials (like PVC, polyethylene and polypropylene) are readily recycled and currently PIPA has recycling programs in Melbourne, Sydney and Brisbane turning waste plastics pipe back into stormwater, DWV and sewer pipe.

These pipes must still meet the performance requirements of the relevant Australian Standards. In these product standards the same performance criteria apply to pipes made from virgin materials as those that include recycled material. The use of recycled material in these products is a great environmental benefit and performance standards are identical.

3. Installation Cost Comparisons

One needs to be particularly careful when considering some of the published cost comparisons between rigid pipe and flexible plastics pipe. Look carefully at the information as it is often very selective in the items covered and pipe types compared. Some areas that have been selectively omitted from the published comparisons include:

• The cost of plant and equipment – often significantly less for plastics pipe options due primarily to the much lighter weight of plastics pipe.
• The labour cost to lay the pipe – only the compaction cost is included. Lifting, cutting, making connections and fittings are elements of the cost structure that are very much in favour of plastics pipe systems.
• The trench conditions nominated do not apply to all rigid pipe classes
• Under roadways compaction is the same for rigid and flexible pipes.
• Laying rate

Locations where plastics pipe systems have distinct advantages include:

• Locations with difficult access or environmentally sensitive areas
• Where native soils can be used such as beach sand
• Aggressive soil environments such as acid sulphate soils or inter-tidal areas
• Deep trenching where light weight pipes can be easily manoeuvred between trench shields and subsequently laid to grade.

The following photographs highlight the attributes that contribute to plastics being cost competitive.

A 6m length of DN375 structured wall Polypropylene drainage pipe
being safely lowered into the trench by hand

Deep excavation requiring trench shields.

4. What is the track record of flexible plastics pipe?

Plastics have been used in pressure and non pressure applications for over 40 years. Plastics pipe systems account for over 75% of the pressure water reticulation pipelines being installed across Australia today and over 90% of the sewer reticulation pipelines.

Both gravity sewer and pressure water pipe systems have significantly more rigorous specifications than drainage in terms of pipe and joint performance. Infrastructure water and sewer systems are highly regulated environments where pipeline system performance is a key indicator for the asset owners. In both sewer and pressure water applications the pipe systems that have been replaced by plastics are poor performing rigid pipe options. The success of plastics pipes is down to their cost effectiveness and significantly better performance than the alternative materials.

In terms of pressure applications concrete pipes are simply not a mainstream alternative. In the non-pressure applications like sewer reticulation flexible plastics pipe systems have essentially replaced the old rigid Vitrified Clay, Asbestos Cement and Concrete systems. These old rigid sewer pipe options comprehensively failed due to pipe cracking, relatively poor joint performance and simply an inability to withstand the rigors of non pressure sewer applications.

The asset owners of pipelines in highly regulated areas where system performance is often independently scrutinised have already made the transition to flexible plastics pipe. The unregulated systems such as drainage are now benefiting from the availability of plastics pipe systems.

5. What is the significance of pipe deflection?

The significance and consequence of pipe deflection is misrepresented in many publications. Flexible pipe systems are designed to accommodate ground movement. Excessive deflection has the potential to impact on the pipeline in two basic areas – the strain generated in the pipe wall and joint performance. Thermoplastics (such as PVC, Polyethylene and Polypropylene) are not strain limited materials ^(2)(3)(4)(5) . Hence from the perspective of deflection leading to excessive strain in the pipe wall - this is simply not a limiting case. Deflection is not a limiting functional parameter.

The selection of a deflection limit is an arbitrary one. "Design long term deflections of 15% are accepted and this is based on the limits of joint performance specification." ⁽²⁾. Deflections have little impact on the flow through pipelines – for example a pipe deflected by 15% will only experience a 5% reduction in flow capability. The most recent developments in this area of specification – ISO/DIS 21138-1 ⁽⁶⁾ recommend an average deflection limit of 10% - in other words recognising that deflections above 10% are acceptable.

Hence the assertion by the concrete pipe industry about flexible plastics pipe in the context of AS/NZS 2566 that "the key measure of this structural integrity is the extent of the deflection that has occurred in the installed pipe" and "failure to detect even one deflection which has exceeded the specified limits could result in catastrophic failure of the pipeline" is erroneous. Exceeding the arbitrary limit of 7.5% does not mean the pipe integrity is at risk and certainly does not mean that "catastrophic failure" is likely.

References

1. Demartini C, Hansen B, and Lee D, "Cracking of stormwater pipes and the significance of construction loads", Pipes Wagga 1999
2. Chapman P G, Croker L, and Menolotto F, "Practical use and performance testing of light weight thermoplastics pipes", Pipes Wagga 2005
3. Janson L E, "Plastics pipes for water supply and sewerage disposal", 4^th ed, 2003
4. Moser A P, Shupe O K, and Bishop R R, "Is PVC pie strain limited after all these years", Buried Plastic Pipe technology, ASTM STP 1093, ASTM, 1990
5. Bishop R R, "Polyvinyl Chloride (PVC) pipe samples exposed to various environments and constant strain", Buried Plastic Pipe Technology, ASTM STP 1093, ASTM, 1990.
6. ISO/DIS 21138-1 "Plastics piping systems for non-pressure underground drainage and sewerage structured wall piping systems of unplasticised poly (vinyl chloride) (PVC-U), polypropylene (PP) and polyethylene (PE) part 1: material specifications and performance criteria for pipes, fittings and system"