Currently, various materials are used in different applications of urban water networks, including ductile iron (DI), steel (ST), prestressed concrete (PSC), glass fiber reinforced polymer (GRP), high-density polyethylene (HDPE), and rigid polyvinyl chloride (uPVC). The aim of this paper is to develop an algorithm for selecting the most appropriate type of pipe in different applications of water supply networks, taking into account design parameters, local experience, environmental conditions, construction, operation, maintenance, and financial evaluation.
Technical evaluation includes examining structural characteristics, environmental conditions, construction, operation, and maintenance. The impact of each of these parameters varies from project to project and depends on the “project intensity factor.” Financial evaluation considers the supply and installation costs of all selected pipe types. The method for selecting the most suitable type of pipe for specific applications in water supply networks is carried out in four stages, as shown in Figure 1:
Stage 1: Elimination of unsuitable options At this stage, an elimination chart is designed to select acceptable pipe types for a specific application. Design parameters and local experiences in using different pipe materials must also be considered.
Stage 2: Technical evaluation Among the pipe materials selected in the previous stage, a technical evaluation is carried out. This includes structural characteristics (service life, resistance to internal pressure, resistance to external pressure, resistance to impact loads), environmental conditions (resistance to soil corrosion, resistance to groundwater corrosion, resistance to internal corrosion, resistance to stray current corrosion), and construction, operation, and maintenance (installation trench width, need for special bedding, need for thrust blocks, ease of pipe connection, ease of leak detection, ease of repair, pipe weight). For each type of pipe, a score from 1 to 5 is assigned based on technical criteria (Table 1).
According to Table 2 and the technical evaluation, HDPE is identified as the best overall pipe material, followed by ductile iron, prestressed concrete, rigid PVC, steel, and finally GRP.
The world is currently facing major environmental challenges such as global warming, environmental pollution, ozone layer depletion, and waste accumulation. Research over the past decades shows that climate change is occurring rapidly and will continue in the future; therefore, immediate action is necessary to reduce the negative impacts of modern lifestyles. The construction industry, despite its vital role in housing and infrastructure development, contributes significantly to environmental pollution, consuming about 40% of global energy, a figure expected to rise to 50% by 2030. Dependence on fossil fuels has led to greenhouse gas emissions and intensified global warming. Consequently, selecting materials with lower embodied energy and sustainable energy sources is crucial to reducing environmental impacts.
Pipes play a key role in the construction industry (urban water supply and sewerage networks) as well as in process industries and oil and gas sectors for fluid transport. Previously, metallic pipes were widely used, but corrosion caused significant damage and economic and environmental costs, making corrosion the second leading cause of pipe failure. As a result, the use of non-metallic materials such as polyethylene and concrete pipes has increased.
Production stage: Carbon steel pipes have significantly higher environmental impacts compared to polyethylene and concrete pipes due to greater raw material consumption. For example, producing one kilometer of carbon steel pipe with a 200 mm diameter results in 105 tons of CO₂ global warming potential (GWP) and requires 36,000 kg of raw materials, while an equivalent polyethylene pipe produces only 5.25 tons of CO₂ and requires 8,500 kg of raw materials. Energy consumption is also critical: manufacturing a 3-meter steel pipe with a 125 mm diameter requires 395 kWh, compared to only 81.5 kWh for a polyethylene pipe of the same size.
Transportation stage: Concrete pipes have the highest GWP during transportation due to their heavy weight, requiring more fuel and energy for trucking. For instance, a concrete pipe with a 400 mm diameter weighs about 134,100 kg and adds 5.92 tons of CO₂ per kilometer, while a polyethylene pipe of 125 mm diameter weighs only 3,800 kg and contributes just 0.066 tons of CO₂ per kilometer—almost 3,000 times less.
Installation stage: Two main installation methods are used: open trench excavation and trenchless technologies (horizontal directional drilling, pipe jacking, microtunneling, spiral drilling). Trenchless methods significantly reduce environmental impacts compared to conventional open trench excavation.
Operation stage: This stage includes pumping (energy-intensive and associated with CO₂ emissions), inspection and maintenance, and emissions from repair and rehabilitation. For steel pipes, internal corrosion increases hydraulic roughness over time, leading to higher friction losses and greater pumping energy. In contrast, HDPE pipes have lower friction coefficients, reducing energy consumption. Over a 50-year lifespan, CO₂ emissions from pumping through HDPE pipes are estimated at 1,491 tons, lower than steel and concrete pipes. Thus, the operation stage, particularly pumping energy, often represents the largest share of total GWP in the pipe network life cycle.