Pipe for Water Supply Selection Principles

Our factory has many years of experience and technology in the production of water supply pipes, and can produce water supply pipes of various materials, such as: pe water pipe, u-PVC water pipe, PEX pipe, PPR pipe. Recently, some customers have asked us how to choose water supply pipes. We have analyzed how to choose water supply pipes for customers from the following aspects.

Selection principle

Safety and reliability

This is the most important principle of building water supply. Building water supply is a pressurized pipe. Once the water leaks and bursts, it will cause losses to buildings and people's property. The safety and reliability of water supply pipes are generally reflected in the following aspects:

(1) Temperature and pressure resistance. The design working pressure of the thermoplastic water supply pipeline system generally refers to the pressure bearing capacity of the plastic pipe when the temperature of the conveying medium is 20°C. When selecting cold water pipes, this value is generally used as the selection criterion, but as the temperature of the transported medium increases and the service life of plastic water supply pipes increases, its pressure bearing capacity will gradually decrease, so thermoplastic pipe for water supply are selected as hot water pipes When using hot water, its long-term bearing capacity at hot water temperature should be considered as the selection criterion; the main material of composite pipes is still based on thermoplastic materials, and metal materials can increase its rigidity and tensile and impact resistance, but seasonal changes may change The pressure bearing capacity of the pipeline, so the composite material pipeline should choose different pipe for water supply materials for conveying cold and hot water.

(2) Linear expansion coefficient.

The linear expansion coefficient of plastic pipe for water supply is much larger than that of metal, and its linear deformation is mainly manifested in the expansion and extension and bending in the axial direction of the pipe. For installation, when the straight-line distance is greater than 20m, the natural compensation method of expansion joints or knuckles should be considered, which is the most important difference between plastic pipe for water supply and metal pipes.

(3) Water hammer resistance (elastic modulus), wall thickness. In the water supply system, due to the opening and closing of valves, the system pressure changes suddenly, which will cause water hammer phenomenon. Severe water hammer phenomenon can lead to bursting and deformation of pipe for water supply. The magnitude of the water hammer pressure is related to the wave velocity of the water hammer, and the wave velocity of the water hammer is related to the elastic modulus, pipe for water supply diameter and wall thickness of the pipe for water supply. The smaller the elastic modulus of the pipe, the larger the pipe diameter, and the thinner the wall thickness can reduce the water hammer. Generally, the water hammer resistance of various plastic pipes is lower than that of steel pipes. Any kind of pipe has its own service life. If it continues to be used beyond its service life, there is a danger of bursting at any time due to performance degradation.

Economy

On the premise of satisfying safe water supply, it is another important principle for users to spend the least amount of money to select pipe materials. Comprehensive price factors are related to many aspects, such as material prices, origin, transportation costs, joints and accessories, etc. Generally speaking, the prices of plastic pipes and composite pipes are higher than those of galvanized steel pipes, but the comprehensive price is not necessarily high. When comparing pipe prices, it is also necessary to compare the prices of pipe for water supply fittings and construction and installation costs. For example, the pipe for water supply joints of thin-walled copper pipes may not be too expensive, but the cost of welding may be more expensive than the pipe joint itself. Copper pipes are also more expensive. This shows that each pipe has its applicable economic position, which must be fully considered when selecting.

Hygienic

Various modifiers, additives, additives, etc. of plastic pipe for water supply, and metal ions dissolved in water by metal pipes (collectively referred to as environmental factors that cause mutagenesis in the human body) may cause adverse effects on human organs. Therefore, plastics without modifiers or metal pipes without heavy metal molecules in the surface coating have good hygienic performance. energy saving

The output of any pipe from raw materials to finished products consumes energy. From a macro point of view, metal pipes consume more energy than plastic pipes. In the composite process, steel-plastic composite pipes that use thermal expansion and spraying composite processes are more than metal pipes. Energy consumption; thick-walled pipes consume more energy than thin-walled pipes; pipes with larger inner surface roughness consume more energy than those with smaller roughness; pipe joints with local diameter reduction consume more energy than diameters, that is, the loss of water head along the course and locally is large. From the perspective of construction technology, electric welding, gas welding, and hot-melt connections consume more energy than brushing twisted teeth.

Sustainable development

Any kind of pipe for water supply can be used for a long time, and one of the most important reasons is that it can be recycled and reused without generating new pollution. Copper pipe for water supply and galvanized steel pipe for water supply are gradually restricted or eliminated because they are easy to corrode and affect water quality. For plastic pipes, most of the waste can be recycled and reused, but cross-linked polyethylene (PEX) waste pipes cannot be reused or degraded. If this problem is not solved, it will be gradually restricted or eliminated sooner or later. If there is a contradiction between the above principles, the principle of safety and reliability should be obeyed first, followed by the principle of sustainable development.

Selection considerations

(1) Building decoration standards. Fully decorated high-end commercial houses should use high-grade pipes, such as copper pipes and stainless steel pipes; while rough houses should use cheap pipe for water supply such as PVC-U or PE pipes. These pipes will be thrown away as construction waste.

(2) The life of the building. Generally, the life span of high-rise buildings is set at 100 years, and that of multi-storey buildings is set at 50 years, and the selected pipes should match it. For the dwelling house that has been occupied, it is very difficult to cut off the water and destroy the decoration as changing the water supply pipe.

(3) Water delivery temperature. According to the applicable cold water pipe and hot water pipe.

(4) Water quality of water delivery. It is distinguished by the delivery of general drinking water and the delivery of clean drinking water.

(5) Use occasions. The pipes in the pump room should use metal pipes due to vibration, water hammer impact and maintenance. Pressurized standpipes and main water supply pipes are like the aorta of the human body, and require high reliability, so metal pipes should be used. The general pressure of the branch pipe entering the household does not exceed 0.6 MPa, and metal pipes or plastic pipes can be used. The pipes in the water tank (pool) are generally metal pipes, which must bear the switching torque of the hydraulic valve.

(6) Laying method. Clear and dark application. Mingfu can be divided into indoor and outdoor. Plastic pipe for water supply should not be exposed outdoors, as they are easily exposed to sunlight and accelerate aging. Some flexible plastic tubes are not suitable for indoor application, and are prone to thermal expansion and cold contraction, bending and deformation.

(7) Pipe diameter. Large-diameter building water supply pipes or metal and plastic composite pipes are neither suitable nor economical due to the large number of consumables and the difficulty in controlling the connection quality.

(8) Joint connection form. The ferrule-type connection is detachable and easy to install, but it is prone to water leakage, especially when used in a hot water system, the joint is easy to loose due to the alternating changes of cold and heat; Good; the socket bonding type is convenient for construction, cannot be disassembled, and the sealing performance is acceptable, but the adhesive requires special use and should be kept away from open flames.

(9) Groove connection, not suitable for small diameters, generally used for large diameter water supply pipes. Generally, PE and PEX-lined steel-plastic composite pipes can be used for grooved connections because of their good plastic toughness and creep properties.

(10) The chance of water leakage in the hot-melt connection is small, but the construction is required to be fast, and the level and verticality must be grasped. Once the overall situation of the connection is determined, it cannot be modified, and the quality of the large-diameter hot-melt is poor. Welding connections are only suitable for copper pipes, and the construction costs are high and there is an open flame.

(11) The threaded connection is only suitable for plastic-lined (coated) plastic-steel-plastic composite pipes, nickel-plated phosphorus alloy steel pipes, and fittings should be inner-injected malleable steel fittings.

(12) Flange connection is only suitable for large diameter pipes.

To sum up, the selection and construction of new building pipe for water supply should consider

(1) The pressure resistance capacity of the pipe for water supply, especially the temperature change will change the pressure resistance capacity of the pipe.

(2) The linear expansion coefficient of the plastic pipe for water supply is much larger than that of the metal pipe, and the temperature compensation device should be installed for the surface-mounted pipe for water supply.

(3) Different parts of the pipeline in the water supply system have different characteristics in the construction and installation, and the pipeline and connection method should be selected according to the performance of the pipeline.

HDPE pipe for water supply and PVC pipe are commonly used in building construction, and are also products that most customers consult. In order for customers to better choose pipe for water, the editor puts the parameter table of hdpe pipe for water supply below for customers' reference.