Frequently Asked Questions About Pipes, Pipelines and Technical Solutions
A Practical Guide for Designers and Contractors
In this section, you will find answers to the most common questions that designers, installers, and contractors face every day when working with sewer networks, pressure pipelines, and drainage systems.
Our technical FAQs help you solve practical on-site challenges, select the right materials, and comply with applicable standards and regulations.
Each answer also highlights which Martoni solution can make a difference to your project.
What is the difference between PP and PE in piping systems?
Polypropylene (PP) and polyethylene (PE) are both widely used thermoplastic materials in piping systems. However, PP stands out for its higher temperature resistance, making it suitable for higher operating temperatures (up to 70–80°C), while PE is generally preferred for applications with lower operating temperatures (typically 40–60°C).
In addition, PP offers greater structural stiffness while maintaining good flexibility, facilitating installation and ensuring long-term stability. Thanks to its high modulus of elasticity, PP allows significantly thinner wall thicknesses than PE, which can, in some cases, make it possible to reduce the pipe diameter.
It is an ideal material for applications requiring chemical resistance, durability, and excellent mechanical performance under load.
What is the allowable bending radius for PP pipes?
PP pipes can also be installed with a curved alignment, provided that the specified minimum bending radii are respected. These values vary depending on the pipe diameter and the installation temperature.
Although PP is less flexible than PE, it still allows installation that can adapt to the route and profile of the terrain.
In case of doubt, it is always recommended to follow the manufacturer’s guidelines to ensure compliance with applicable technical standards.
Why choose unfilled PP pipes?
Unfilled PP (without mineral fillers or reinforcing additives) is often the preferred choice for several reasons:
- It offers superior mechanical properties and better fatigue resistance;
- It is fully recyclable;
- It provides more uniform elastic behaviour, without the risk of brittleness associated with filler materials.
Pure PP pipes ensure more consistent long-term performance, particularly in sewer networks and infrastructure systems exposed to temperature fluctuations and dynamic loads. Compared with PE, PP provides greater dimensional stability and higher long-term performance.
What is the temperature resistance of PP?
Polypropylene is a material that remains thermally stable up to 80°C under continuous operating conditions, while also being able to withstand short-term temperature peaks above this value. This makes it an ideal choice for systems carrying hot fluids or operating in environments exposed to elevated temperatures.
Unlike PE, which begins to lose stiffness at temperatures above 50–60°C, PP maintains its mechanical properties, reducing the risk of deformation and structural creep over time.
Are PP pipes resistant to UV radiation?
Yes, PP pipes intended for outdoor use are stabilised with specific UV-resistant additives. For example, our orange-coloured pipes are designed to provide long-lasting protection against solar exposure, preventing premature degradation before installation.
For applications involving continuous exposure to sunlight, BRAVO WHITE is the ideal solution to ensure long-term weather resistance. Thanks to its innovative compound, thermal expansion is reduced and the surface remains protected from deterioration, preserving its appearance and performance over time.
PE pipes are typically pigmented black with carbon black to improve UV resistance, whereas properly stabilised PP can provide effective UV protection even without black pigmentation.
How does PP perform in terms of thermal expansion?
PP has a linear thermal expansion coefficient of approximately 0.14 mm/m·K, which is lower than that of PE. This means that PP expands less when exposed to temperature variations, making it more dimensionally stable and particularly suitable for long pipeline runs and buried installations subject to thermal fluctuations.
Thanks to its innovative compound, BRAVO WHITE offers an even lower linear thermal expansion coefficient of approximately 0.06 mm/m·K.
This results in lower stress on joints and anchoring systems, while also simplifying the design and management of thermal expansion.
What do the short-term and long-term modulus of elasticity values indicate for PP?
PP, like all plastic materials, is viscoelastic, meaning that it undergoes deformation over time when subjected to a load. For this reason, two different parameters are considered:
- Short-term modulus of elasticity: used to evaluate the material’s response to impacts and sudden loads;
- Long-term modulus of elasticity: essential for assessing performance under continuous loads, such as soil pressure acting on buried pipelines.
PP offers an excellent balance between stiffness and controlled flexibility, ensuring long-term durability even under constant mechanical stress. PE, which is generally more flexible, tends to deform more easily under sustained loading.
Do PP pipes contain halogens or harmful additives?
No, PP pipes used for cable protection or drainage applications do not contain halogens or toxic substances. This makes them safer in the event of a fire, as they generate lower emissions of harmful gases.
In addition, PP is fully recyclable, contributing to a reduced environmental impact and supporting circular economy principles.
How do PP pipes respond to external loads and stresses?
PP pipes are flexible yet structurally strong. Their ability to slightly deform under load allows external pressures to be distributed through the pipe-soil system, preventing stress concentrations on the pipe wall itself.
Unlike rigid pipes, which transfer loads to specific points, flexible PP pipes work together with the surrounding soil to create a stable structural system. This behaviour reduces the risk of cracking and contributes to the long-term durability of the entire pipeline network.
How do PP pipes withstand cleaning operations and hydraulic stresses?
Thanks to the smooth inner surface of PP, these pipes provide excellent self-cleaning properties, helping to reduce the accumulation of deposits and maintain efficient flow conditions.
PP pipes are highly resistant to high-pressure cleaning operations (up to 200 bar) and retain excellent hydraulic performance even when subjected to slight deformation.
In addition, the molecular structure of PP provides outstanding abrasion resistance and resistance to the chemicals commonly used in sewer network maintenance, ensuring long-term reliability and performance.
Why are flexible pipes such as PP increasingly preferred today?
Flexible PP pipes can adapt to ground movements, compensate for installation tolerances, variations in soil conditions, and unexpected overloads. Their ability to deform in a controlled manner enhances the long-term reliability of the pipeline system.
Rigid pipes, on the other hand, are generally more susceptible to cracks and failures caused by settlement or concentrated loads. For this reason, PP represents a safe and modern solution for durable and resilient infrastructure.
What is the expected service life of a PP piping system?
PP piping systems are designed for an expected service life of more than 50 years and, when properly installed and maintained, can often achieve a service life of up to 100 years.
Throughout their operating life, the material retains its mechanical and chemical properties, ensuring long-term reliability, structural integrity, and consistent performance even under demanding service conditions.
Are socket joints in PP piping systems reliable?
Yes, rubber-sealed socket joints used in PP piping systems are designed to provide watertight performance even in the presence of pipe deformation of up to 30%.
Welding is not required to ensure leak-tightness: socket systems offer flexibility, resistance to chemical agents, and long-term durability, while also simplifying installation and maintenance operations.
However, to achieve the expected performance and service life, it is essential to follow the manufacturer’s installation instructions and recommended installation practices.
Are PP pipes impermeable to radon?
Yes. According to Swiss health guidelines, a material can be considered radon-tight when it combines sufficient wall thickness with very low gas permeability.
Thanks to their thick walls and sealed joints equipped with elastomeric gaskets, PP piping systems meet the requirements to be considered impermeable to radon diffusion.
This characteristic makes PP pipes particularly suitable for underground applications where protection against soil gases, including radon, is an important design consideration.
The product range includes PP-HM and PVC-U pipes and fittings, available in both single-wall and triple-layer co-extruded versions. FOX triple-layer PVC-U pipes feature smooth walls and high resistance to abrasion, temperature variations, and chemical agents. They comply with EN 13476-2 and are PSV-certified, containing 35% recycled material.
The BRAVO GREEN PP-HM system, manufactured with at least 25% recycled material, complies with EN 1852-1 and is available in SN8, SN12 and SN16 stiffness classes, in diameters ranging from 110 to 630 mm.
Completing the range, EDILFOX GREEN pipes combine recycled PVC-U (25%) with PSV certification and are specifically designed for building drainage applications. For indoor building systems, the TALENTO single-wall PVC-U system (EN 1329-1) ensures efficient wastewater drainage.
Martoni has adopted a strong sustainability strategy. Through products such as FOX, BRAVO GREEN and EDILFOX GREEN, the company aims to reduce environmental impact by using PSV-certified pre- and post-consumer recycled materials in compliance with the Minimum Environmental Criteria (CAM). Highly advanced manufacturing facilities allow multilayer pipes to be co-extruded in a single production cycle, ensuring outstanding quality, durability (over 100 years) and a significant reduction in CO₂ emissions, estimated at more than 5,000 tonnes saved per year.
In terms of certifications, Martoni has achieved important recognitions such as ISO 9001 (Quality Management) and ISO 14001 (Environmental Management), as well as the prestigious ESG Gold 2024 rating, confirming its commitment to operational excellence and environmental sustainability.
The company operates through an integrated business model, ranging from technical consultancy and 24/7 manufacturing to efficient logistics, fast deliveries throughout Italy and France, and on-site technical support, fully aligned with its values of collaboration and shared growth.
Martoni strongly believes in the compatibility between pipes and fittings systems, where complete component integration is synonymous with reliability, ease of installation and reduced risk of malfunction.
The company’s vision — “Road to Zero Impact” — combines advanced technologies, circular economy principles and high performance to deliver reliable, sustainable and efficient piping solutions for today’s and tomorrow’s infrastructure.
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