The Standardized Selection of Pipes and Fittings in Residential Community Water Supply Projects

Abstract

The safe operation of residential community water supply systems is closely tied to the proper selection of pipes and fittings. This study examines the technical regulations designed to enhance the quality and efficiency of urban residential water supply systems and summarizes the requirements for mainstream pipe materials—such as ductile iron, stainless steel, and polyethylene—across different application scenarios. The findings show that pipe selection must account for hydraulic conditions, corrosion resistance, sanitary safety, service life, and economic feasibility, while fitting selection should ensure pipe compatibility and reliable installation. A standardized selection system can improve water quality safety, reduce pipe network leakage rates, and extend system service life, thereby providing scientific guidance for residential community water supply projects. Residential community water supply systems are a vital component of urban water infrastructure, and their safe, stable operation is essential to ensuring the quality of domestic water for residents. With rapid urbanization, many aging residential communities urgently require renovation of their water supply systems. As core components, pipes and fittings directly influence water quality, operational stability, and service life. Currently, a wide range of pipe materials are used in residential water supply projects in China, but inconsistent selection standards have resulted in uneven construction quality and difficulties in maintenance. Drawing on the Technical Specifications for Improving the Quality and Efficiency of Building and Community Water Supply Systems, this study systematically analyzes the selection standards for pipes and fittings in residential water supply projects and explores technical approaches to achieving standardized selection. This research aims to provide scientific guidance for the renovation and new construction of residential water supply systems.

1. Types and Characteristics of Pipes and Fittings in Residential Community Water Supply Systems

1.1 Common Pipe Materials and Their Characteristics

Residential community water supply systems use a variety of pipe materials, which can be broadly classified into two categories: metallic and non-metallic. Metallic pipes primarily include ductile iron, stainless steel, copper, and stainless steel-lined composite steel pipes, all of which are recognized for their high strength and excellent pressure resistance. Non-metallic pipes primarily include polyethylene (PE), polypropylene (PPR), and steel–plastic composite pressure pipes, which are lightweight, easy to install, and highly resistant to corrosion. Because these materials differ in mechanical properties, hydraulic performance, corrosion resistance, and service life, their selection should be based on the specific application scenario. Table 1 summarizes the key characteristics and typical application scenarios of commonly used pipe materials in residential water supply systems, providing a reference for proper pipe selection.

1.2 Types and Functions of Pipe Fittings

Pipe fittings in residential water supply systems can be classified into four categories: connection fittings, control fittings, metering fittings, and protective fittings.

Connection fittings include flanges, compression fittings, and hot-melt fittings, which are used to join different pipe sections or materials, and the chosen connection method should be compatible with the specific pipe type.

Control fittings mainly consist of various types of valves, with the material and design selected according to the pipe diameter and the required flow control.

Copper gate valves are appropriate for small-diameter pipes (15–50 mm), whereas elastic, soft-sealed gate valves are suitable for medium- and large-diameter pipes (50–400 mm), with valve stems made of stainless steel, grade 2Cr13 or higher.

Metering fittings mainly consist of water meters, with intelligent, remote-controlled models recommended, featuring Class 2 accuracy and an IP68 protection rating, and installed in locations that allow easy reading and maintenance.

Protective fittings include backflow preventers, filters, and water hammer eliminators, with backflow preventers designed for low resistance and a maximum head loss of ≤0.03 MPa.

Adjustable pressure-reducing valves are used to ensure the safe and stable operation of the water supply system.

Table 1. Characteristics and Application Scenarios of Common Residential Water Supply Pipes

2. Basic Principles for Selecting Pipes and Fittings

2.1 Safety Principle

The selection of pipes and fittings for residential community water supply projects must prioritize safety to ensure the hygienic quality and potability of drinking water. All water-related products must comply with the national standard GB/T 17219: Safety Evaluation Standard for Drinking Water Transmission and Distribution Equipment and Protective Materials and obtain a water-related product hygiene license from the relevant provincial health authority. The inner surfaces of pipes should be smooth, non-toxic, and free from any substances that could cause secondary contamination, while metal pipes should have food-grade epoxy coatings for internal corrosion protection with a minimum thickness of 0.3 mm. Plastic pipes must be manufactured from virgin materials, with recycled materials strictly prohibited. Rubber seals should be made of ethylene propylene diene monomer (EPDM), and materials that could contaminate water, such as asbestos or graphite, are not allowed. Pipes and fittings should also include safety features such as waterproofing, fire resistance, moisture protection, sun shielding, lightning protection, and earthquake resistance to ensure the system operates safely and reliably.

2.2 Durability Principle

The durability of pipes and fittings directly influences the long-term reliability of a water supply system. Metal pipes must have effective corrosion protection on both their internal and external surfaces. For example, ductile iron pipes should undergo rust removal, zinc spraying, and a highly chlorinated polyethylene coating for external corrosion protection, while connections between dissimilar materials must be electrically isolated to prevent galvanic corrosion. Pipes must be capable of withstanding the system’s maximum operating pressure, possess adequate compressive strength, and resist external loads. Plastic pipes should be assessed for UV aging, and those exposed outdoors must be shielded from direct sunlight; in cold regions, water supply pipes should be insulated to prevent freezing. Flexible joints and rubber seals should be routinely inspected and replaced to prevent leaks from aging or deterioration, and a properly matched combination of pipes and fittings can extend system service life while reducing maintenance frequency.

2.3 Economic Principle

The selection of pipes and fittings should account for the full lifecycle cost, including initial investment, operation, and maintenance, as metal pipes such as ductile iron and stainless steel incur higher material and installation costs but provide a longer service life. Plastic pipes, such as PE and PPR, offer lower upfront costs but generally have a shorter service life compared to metal alternatives. The roughness of a pipe’s inner wall impacts hydraulic performance, with smooth-walled pipes, such as stainless steel and PE, offering lower flow resistance and reduced energy consumption. In contrast, aged galvanized steel pipes may develop scaling, which increases flow resistance and raises energy consumption. High-quality pipes and fittings with low failure rates help reduce maintenance and replacement costs, while investing in accessories such as valves and water meters facilitates zoning management and leakage control, enhancing long-term economic efficiency. The choice of anti-corrosion treatments, sealing materials, and connection methods also affects overall cost-effectiveness.

2.4 Principle of Applicability

Pipe and fitting selection must account for project-specific conditions to ensure system suitability and compatibility. For outdoor buried pipes subjected to soil loads, ductile iron pipes, plastic-coated stainless steel pipes, or polyethylene (PE) pipes are recommended. For exposed outdoor pipes subject to temperature fluctuations and UV exposure, stainless steel or steel-plastic composite pressure pipes are recommended. For indoor pipes, materials such as stainless steel or PPR can be selected based on the building type, while plastic pipes should be avoided for water supply risers in high-rise buildings due to high operating pressures. Different pipe materials require compatible connection methods, for example, rubber ring joints for ductile iron pipes and press-fit or flange connections for stainless steel pipes. In regions with extreme climates, low-temperature-resistant materials and antifreeze measures are necessary. Coastal areas require corrosion-resistant materials. In regions with extreme climates, pipes should be made of low-temperature-resistant materials and equipped with antifreeze measures, while coastal areas require materials with enhanced resistance to salt-induced corrosion.

3. Selection Standards for Pipes and Fittings in Different Locations

3.1 Outdoor Buried Pipes and Fittings

Outdoor buried pipes form the backbone of residential water supply systems and must withstand substantial soil pressure and external loads, demanding high strength and excellent corrosion resistance. Recommended materials include ductile iron, plastic-coated stainless steel, and polyethylene (PE) pipes.

Ductile iron pipes:  should have a spheroidization rate of ≥85%, a pipe wall thickness of ≥K9, and a fitting wall thickness of ≥K12. Flexible socket-and-spigot joints with rubber rings are recommended for connections.

Ductile iron pipes: should have a spheroidization rate of ≥85%, a pipe wall thickness of ≥K9, and a fitting wall thickness of ≥K12. Flexible socket-and-spigot joints with rubber rings are recommended for connections.

Polyethylene (PE) pipes: should be made of PE100-grade material. For diameters ≤63 mm, use SDR11 with a pressure rating of 1.6 MPa; for diameters >63 mm, use SDR17 with a pressure rating of 1.0 MPa.

Valves: Buried valves should be resilient, soft-sealed gate valves with stems made of at least 2Cr13 stainless steel. Drain valves should have a diameter equal to ¼–⅓ of the main water supply pipe and be installed at low points and pipe network termini.

Fire hydrants: should be made of ductile iron, with operating rods constructed from stainless steel or copper.

Installation: buried plastic pipes should be equipped with tracer devices and warning tape, and the burial depth should generally be at least 0.7 m.

3.2 Outdoor Exposed Pipes and Fittings

Pipes installed outdoors are exposed to environmental challenges such as temperature fluctuations, UV radiation, and precipitation, which require the use of durable, corrosion-resistant materials. Recommended options include stainless steel pipes, stainless steel–lined composite pipes, and steel–plastic composite pressure pipes.

Pipes: should be made of food-grade stainless steel with a minimum corrosion resistance of S30408. For pipes with diameters ≤80 mm, threaded connections are recommended, while larger pipes may use grooved connections.

Supports: should be evenly spaced and equipped with adjustable expansion and collision-avoidance features.

Material Isolation: Implement measures to prevent electrochemical corrosion between dissimilar materials.
Valves: Exposed gate valves or butterfly valves are recommended; wafer-type butterfly valves may be used in space-constrained installations.

Protection: Avoid direct sunlight by providing shading or insulation as needed. In freezing regions, apply antifreeze measures, and ensure exterior piping is equipped with lightning protection.

3.3 Indoor Piping and Fittings

Indoor piping constitutes the terminal network of the water supply system and directly impacts user experience. Recommended materials include copper, stainless steel, steel-plastic composite pressure pipes, PPR pipes, and stainless steel-lined composite steel pipes.

Copper Pipes: Offer excellent antibacterial properties.
Stainless Steel Pipes: Thin-walled pipes can be joined using double clamps.
PPR and Hot-Melt Pipes: Suitable for indoor hot and cold water systems; hot-melt pipes provide superior sealing for hot water applications.

Installation Requirements: Indoor pipes should not be concealed within walls or floors; public risers should be installed in pipe shafts or light wells.
Valves: Ball valves and angle valves are recommended, with copper valves preferred for small-diameter pipes.

Water Meters: Smart remote water meters are preferred. Submeters in multi-story buildings must be centrally installed, and high-rise submeters arranged in layers.
Auxiliary Equipment: Systems shall include pressure-reducing valves, backflow preventers, filters, and automatic air vent valves at the top of high-rise risers.

4. Establishing a Standardized Selection System for Pipes and Fittings

4.1 Technical Guidelines for Standardized Selection of Pipes and Fittings

The technical guidelines for standardized selection of pipes and fittings in residential water supply projects shall define a comprehensive parameter system, including material properties, specifications and dimensions, connection methods, and application conditions. A classification matrix should be developed for different application scenarios, including ductile iron, stainless steel, and polyethylene (PE) pipes, systematically aligning their technical parameters with compatible accessories. Pipe selection should define both rigidity and elasticity indicators. Rigidity indicators encompass essential requirements such as material safety, pressure-bearing capacity, and service life. Elasticity indicators reflect considerations such as ease of construction and maintenance costs. The guidelines should also establish compatibility assessment standards for pipes and accessories, specifying transition connections between different materials to prevent localized system failures due to material mismatch. Additionally, the guidelines should incorporate zoning standards for community water supply systems, clarifying pipe selection for mains, distribution branches, and household connections to establish a clear hierarchical selection system. For special environmental conditions, differentiated selection strategies should be developed to ensure that pipes and accessories are suitable for various environments.

4.2 Quality Control System for Pipe and Fitting Selection

A robust quality control system is essential to ensure the proper implementation of standardized pipe and fitting selection. The system should encompass the entire lifecycle, from product manufacturing to on-site acceptance and installation. Factory inspection standards should require manufacturers to conduct both physical and sanitary performance tests for each production batch. Physical performance tests must comply with relevant national standards, while sanitary performance tests should cover at least 1% of the total sample size.

On-site acceptance inspections should verify appearance quality, markings, specifications, dimensions, material certifications, and performance reports.

Sampling should verify key parameters, including pipe wall thickness, spheroidization rate, and SDR value. Health permits and water-related product test reports must be complete and valid.

Construction quality control should incorporate supervisory witness points and a hidden work acceptance system, with particular attention to critical processes such as pipe connections, anti-corrosion treatment, bracket installation, and pressure testing.

During system commissioning, functional testing standards—including water pressure testing, leak-tightness testing, flushing, and disinfection—should be strictly followed to ensure the water supply system meets design requirements.

4.3 Information Management of Pipe and Fitting Selection

The information management of pipe and fitting selection in residential community water supply projects serves as an effective means to implement standardized selection, improving efficiency and accuracy via digital technologies. The core of this system is the establishment of a comprehensive product database encompassing all standard-compliant pipes and fittings on the market, including technical parameters, performance characteristics, applicable scope, cost information, and supplier qualifications. The database should support parametric query functionality, allowing designers to input key project requirements and automatically generate a list of qualified products. Building Information Modeling (BIM) technology is essential for visually representing 3D piping layouts, automatically identifying clashes, calculating material requirements, and integrating with the product database to enable accurate selection of pipes and fittings. Intelligent selection systems shall recommend optimal pipe and fitting combinations according to project requirements and budget constraints, considering safety, durability, cost-effectiveness, and applicability. Information management shall cover the full lifecycle of pipes and fittings, from procurement through installation and maintenance, implementing an IoT-based tracking system for comprehensive oversight.

5. Conclusion

The standardized selection of pipes and fittings in residential community water supply projects is crucial for ensuring safe, reliable, and stable system operation. Research indicates that selecting appropriate pipes and fittings requires careful consideration of technical performance, economic efficiency, and their impact on water quality and safety. The standardized selection of pipes and fittings shall adhere to principles of safety and reliability, energy conservation and environmental protection, cost-effectiveness, and intelligent management, utilizing the most suitable pipes and connection methods for different application scenarios. Establishing a comprehensive selection system—including technical guidelines, quality control, and information management—is essential for enhancing both the quality and efficiency of residential water supply projects. Future studies should focus on the development of new pipe materials, the implementation of intelligent monitoring and management systems, and the provision of technical guidance to improve water quality and overall system reliability.