In modern water supply systems, plastic pipes are gradually replacing traditional metal pipes and becoming the mainstream choice due to their excellent performance and economy. Among them, high-density polyethylene (HDPE) and polyvinyl chloride (PVC) pipes are the two core materials, each showing unique advantages and application potential. This article will deeply analyze the physical and chemical properties, production process, connection technology, application scenarios and future development trends of these two plastic pipes, providing a scientific material selection basis for engineering design, municipal construction and pipe network reconstruction.
The water supply pipeline system is an important part of urban infrastructure, and its material selection is directly related to water quality safety, water supply efficiency and pipe network life. Traditional metal pipes have exposed many problems in practical applications: cast iron pipes and steel pipes are prone to electrochemical corrosion, especially in areas with low soil resistivity or high groundwater levels; copper pipes are corrosion-resistant but expensive, and there is a problem of copper ion precipitation affecting water quality; galvanized steel pipes face the risk of zinc layer shedding and pipe blockage.
In contrast, plastic pipes fundamentally solve the corrosion problem. Their chemical corrosion resistance prevents the pipe wall from gradually thinning due to reaction with soil or water substances, thereby greatly extending the service life. HDPE and PVC pipes have become the mainstream choice in modern water supply systems due to their unique performance characteristics and economic benefits.
According to industry data, my country's HDPE pipe production will reach 5.875 million tons in 2023, demand will reach 5.669 million tons, and the market size will be 57.438 billion yuan. It is expected that in 2024, it will increase to 6.193 million tons, 5.981 million tons, and 60.719 billion yuan, respectively. Although the growth of PVC pipes is relatively slow, it still maintains a stable demand in specific application areas. This growth trend is mainly driven by three factors: first, the global urbanization process is accelerating, and there is a strong demand for new water supply pipelines; second, the renovation and upgrading of old pipelines is imminent; third, environmental protection regulations are becoming increasingly stringent, promoting the replacement of traditional materials.
As the core material in modern water supply systems, HDPE pipes have comprehensive performance advantages. From the perspective of molecular structure, HDPE is a polymer material formed by the polymerization of ethylene monomers. Its linear molecular chain and highly crystalline structure give the material excellent mechanical strength and chemical stability.
Corrosion resistance is one of the most significant advantages of HDPE pipes. Unlike metal pipes, HDPE does not undergo electrochemical corrosion or rust, and can resist the erosion of most chemical substances in the soil, including acid, alkali, salt and other media. This feature is particularly important in coastal areas or industrial areas. Actual engineering cases show that in the long-distance water supply project of the Nalinggelexi Water Source in Qinghai, the use of HDPE pipes saves about 20% of the total investment compared to the metal pipe solution, and no additional anti-corrosion treatment is required.
In terms of physical properties, HDPE pipes also perform well. Its low-temperature brittleness temperature is extremely low (-60°C) and its high-temperature tolerance is 60°C, enabling it to adapt to a wide range of temperatures from severe cold to extreme heat. The flexibility of HDPE pipes is also a highlight, with an elongation at break of more than 350%, which enables them to adapt to geological activities such as foundation settlement and earthquakes. Surveys after the Hanshin earthquake in Japan showed that the damage rate of water supply systems using HDPE pipes was significantly lower than that of rigid pipe systems.
The inner wall of HDPE pipes is extremely smooth, and the Manning coefficient is only 0.009, which is much lower than that of concrete pipes (0.013) and metal pipes (0.012). This hydraulic characteristic makes the flow rate of HDPE pipes about 30% higher than that of reinforced concrete drainage pipes under the same pipe diameter conditions. For long-distance water supply projects, this means that pumping energy consumption can be significantly reduced, achieving energy conservation and environmental protection.
The reliability of connection technology is directly related to the integrity of the water supply system, and HDPE pipes have made revolutionary breakthroughs in this regard. Hot-melt butt welding and electric fusion welding technology can completely melt the two sections of pipes at the interface into one, forming a molecular-level connection, whose strength even exceeds the pipe body itself. This connection method fundamentally solves the stubborn problem of leakage in traditional pipe joints and realizes a truly zero-leakage system. Comparative data shows that the leakage rate of the pipeline system connected by rubber rings is usually 15-25%, while the HDPE hot melt connection system can control the leakage rate below 2%.
The lightweight characteristics of HDPE pipes greatly simplify the transportation and installation process. Under the same specifications, the weight of HDPE pipes is only 1/8 of that of steel pipes and 1/24 of that of concrete pipes, which greatly reduces the transportation cost and installation difficulty. In areas where space is limited or machinery cannot enter, HDPE pipes can be installed using non-excavation technologies such as "drag pipe method" to reduce damage to the ground environment.
It is worth mentioning that HDPE pipes also perform well in terms of hygienic performance. Food-grade HDPE materials will not release harmful substances, will not breed bacteria, will not produce rust pollution, and ensure the safety of drinking water quality. The HDPE pipe for water supply produced by Bestom is non-toxic and not easy to scale, and has passed strict hygienic performance tests.
As another major category of plastic water supply pipes, PVC pipes occupy an important position in the global water supply system with their unique performance characteristics and cost advantages. Compared with HDPE pipes, PVC pipes exhibit higher rigidity and dimensional stability, making them particularly suitable for pressure water supply scenarios that require higher ring stiffness.
PVC pipes are used in various forms in the water supply field, mainly including ordinary PVC-U pipes, PVC-UH high-performance pipes and modified PVC pipes. Among them, PVC-UH (ultra-high performance polyvinyl chloride) pipes represent the highest level of current PVC water supply pipe technology. Bestom's PVC pipes for fresh water use high-quality PVC mixed ingredients and a unique steel skeleton sealing ring socket structure, which has more stable performance and more reasonable cost.
In terms of physical properties, PVC pipes exhibit a series of characteristics. Its tensile strength is usually in the range of 50-60MPa, which is higher than the 20-30MPa of HDPE pipes, which makes PVC pipes perform well when subjected to internal pressure. The Vicat softening temperature of PVC pipe is about 80℃, which is higher than 120℃ of HDPE pipe, indicating that it has better shape retention ability in high temperature environment. However, the low-temperature brittleness of PVC is more obvious, and the brittle temperature is about -10℃, which is much higher than -60℃ of HDPE, which limits its application in cold areas.
PVC pipes are also excellent in chemical corrosion resistance, and can resist the erosion of most acids, alkalis, and salts, and will not suffer from electrochemical corrosion like metal pipes. However, compared with HDPE, PVC has weaker resistance to certain organic solvents (such as ketones, esters and aromatic hydrocarbons). In practical applications, PVC pipes are particularly suitable for conveying water bodies with a pH value in the range of 2-12, covering almost all normal water supply conditions.
In terms of connection technology, PVC pipes mainly use two methods: socket-type rubber ring connection and solvent bonding. Socket connection is easy and quick to install, allows a certain deflection angle, and adapts to small deformation of the foundation; solvent bonding achieves permanent connection through chemical fusion, which is suitable for small-diameter pressure pipes. Compared with the hot-melt welding of HDPE, the connection method of PVC is slightly inferior in reliability and sealing, but it is simple to operate and does not require special equipment.
Economic efficiency is the most prominent competitive advantage of PVC pipes. Due to the relatively low price of PVC resin and low processing energy consumption, the market price of PVC pipes is usually 15-30% lower than that of HDPE pipes of the same specification. In large-scale water supply network projects, this price difference can be converted into considerable cost savings. In addition, the rigidity of PVC pipes makes it less demanding to backfill soil when buried, further reducing construction costs.
In terms of health and safety, modern PVC water supply pipes are fully compliant with drinking water standards. By using non-toxic stabilizers (such as calcium-zinc composite stabilizers) instead of traditional lead salt stabilizers and strictly controlling monomer residues, PVC-UH pipes have solved the problem of heavy metal precipitation that may have existed in the early stage.
In the design and renovation of water supply systems, the scientific selection of pipe types is related to the success or failure of the project. As two mainstream plastic pipes, HDPE and PVC pipes each have their own unique performance characteristics and scope of application.
1. The comparison of mechanical properties shows that the two materials have their own emphasis. HDPE pipes show excellent flexibility and impact resistance, with an elongation at break of more than 350%. They can absorb external force impact through elastic deformation, which is particularly suitable for geologically unstable areas. PVC pipes have higher stiffness and strength, with a bending modulus of about 10 times that of HDPE. They deform less when subjected to internal pressure and are more suitable for occasions requiring higher ring stiffness.
2. In terms of temperature adaptability, HDPE pipes have obvious advantages. Its operating temperature range is -60℃ to 60℃, and its low-temperature brittle point is only -70℃. It will not crack even when constructed in severe cold environments. In contrast, the low-temperature brittleness of PVC pipes is more prominent. When the temperature is below -10℃, the impact strength decreases significantly, and installation and use are subject to seasonal restrictions.
3. Chemical corrosion resistance is a common advantage of both plastic pipes, but the degree is different. HDPE pipes are almost not corroded by any acid, alkali and salt solutions, and can even tolerate some organic solvents; PVC pipes also have good resistance to inorganic acids, alkalis and salts, but are more sensitive to some organic solvents. In oxidizing environments (such as chlorine-containing disinfectants), HDPE performs slightly better than PVC.
4. Hydraulic properties have an important impact on the energy consumption and delivery capacity of water supply systems. The inner wall of HDPE pipes is extremely smooth, with a Manning coefficient of 0.009 and low hydraulic friction. After long-term use, it can still maintain a high flow capacity. The inner wall of PVC pipes is slightly less smooth (Manning coefficient 0.010-0.011), but it is still better than traditional pipes.
5. In terms of connection technology, hot-melt butt welding and electric fusion welding of HDPE pipes can form molecular-level fusion, realize a true zero-leakage system, and the joint strength is higher than the pipe body itself. PVC pipes mainly use rubber ring socket connection and solvent bonding. The former allows a certain displacement but has relatively poor sealing. The latter can form a permanent connection but has higher requirements for operation.
6. Life cycle cost is a key consideration in selection decisions. The initial investment of PVC pipes is usually 15-30% lower than that of HDPE pipes of the same specifications, which is obviously attractive in projects with limited budgets. However, HDPE pipes often have more advantages in life cycle cost calculations due to their longer service life (usually 10-15 years longer than PVC pipes), lower leakage rate and maintenance requirements.
With the acceleration of global urbanization and increased infrastructure investment, the market prospects for HDPE and PVC plastic water supply pipes are broad.
