the following mainly introduces several common pipes and their characteristics.

1. Steel pipes

Steel pipes include ordinary steel pipes, galvanized steel pipes and seamless steel pipes. Ordinary steel pipes are used for non-domestic drinking water pipes or general industrial water supply pipes. The surface of steel pipe is galvanized (produced by hot-dip galvanizing process) to prevent rust and corrosion, so as not to affect the water quality. It is suitable for drinking water pipes or some industrial water pipes with high water quality requirements. Seamless steel pipe is used in high pressure pipe network, and its working pressure is above 1.6MPa.

the connection methods of steel pipes include threaded connection, welding and flange connection. Threaded connection is the connection with threaded pipe fittings. Fittings are mostly made of malleable cast iron, which is divided into galvanized and non-galvanized, and its corrosion resistance and mechanical strength are great. At present, there are few steel fittings. Galvanized steel pipes must be connected with threads, and their fittings should also be galvanized fittings. This method is often used for exposed pipelines. Welding is to connect two sections of pipes by welding machine and covered electrode. Advantages are tight joints, no water leakage, no need for accessories and rapid construction. But it can't be disassembled. Welding is only applicable to galvanized steel pipes. This method is mostly used for concealed pipelines.

Flanges are connected to pipelines with larger diameters (more than 51m). Flanges are often welded (or screwed) to the pipe ends, and then the two flanges are connected by bolts, so that the two pipelines are connected together. Flange connection is generally used to connect valves, check valves, water meters, pumps, etc., as well as pipe sections that need to be disassembled and overhauled frequently.

2. Water supply plastic pipes

The most commonly used water supply plastic pipes are water supply rigid polyvinyl chloride pipe (UPVC) and water supply polypropylene pipe (PP pipe). In addition, there are polyethylene (PE) pipes, which are suitable for conveying water with the water temperature not exceeding 41℃, and their relevant standards follow the provisions of GB/T13663, Polyethylene (PE) Pipe for Water Supply; Cross-linked polyethylene (PE-X) pipe: polybutylene (PB) pipe, which is suitable for conveying water at a water temperature of-21 "-91℃. They all have strong chemical stability, corrosion resistance, no corrosion from acid, alkali, salt, oil and other media, smooth pipe wall, good hydraulic performance, light weight and convenient processing and installation. But the shortcomings of * * * are poor temperature resistance and low strength. Therefore, it is also limited in use.

water supply rigid polyvinyl chloride pipe (UPVc), the temperature of water delivery shall not exceed 45℃. UPVC pipe generally adopts socket connection, in which socket bonding is suitable for pipe diameter of 21 ~ 1611 m; Rubber ring connection is suitable for pipe diameter greater than or equal to 63mm; The connection with metal pipe fittings, valves, etc. adopts thread or flange connection.

water supply polypropylene pipe (PP pipe) is suitable for systems with working pressure not greater than 1.6Mpa and working temperature not greater than 71℃. Water supply polypropylene pipe is connected by hot melt socket. When connecting with metal pipe fittings, polypropylene pipe fittings with metal inserts are used as the transition, and the pipe fittings are connected with polypropylene pipes by hot-melt sockets and with metal pipe fittings by threads.

3. PVC pipe

is actually a kind of plastic pipe, and the joints are generally glued. It is difficult to be used as a hot water pipe because of its poor frost resistance and heat resistance. Pipes are easy to break and deform when heated. In most cases, PVC pipes are suitable for electrical threading pipes and drainage pipes.

4. PPR pipe

PPR pipe is sanitary and non-toxic, and can be directly used in pure water and drinking water pipeline systems. Corrosion-resistant, not easy to scale, eliminating the secondary pollution caused by corrosion and scaling of galvanized steel pipes. Heat-resistant, can transport hot water with the temperature below 71'C for a long time, and can withstand the instantaneous high temperature of 95℃. The fluid resistance in the pipeline is small, the inner wall of the pipe is smooth, and it is not easy to scale, and the fluid resistance is much lower than that of the metal pipeline. The length of each section of the pipeline is limited, and it cannot be bent for construction. If the pipeline is laid for a long distance or there are many corners, a large number of joints will be used in the construction, and the pipe is cheap but the price of accessories is relatively high. PPR plastic pipe itself is non-toxic and meets the hygienic requirements, but it has no self-cleaning function and bacteria killing function. In the specific environment of domestic water use, the pollution of water source, the backward technology of waterworks and the outdated and unreasonable pipe network make domestic PPR water pipes become the gathering place of secondary pollutants and the breeding ground of bacteria, which seriously threatens human health. A health report of some cities in China in recent years reveals that a large number of diseases and cancers are related to the quality of domestic tap water and the wrong choice of water pipe materials. It is an undisclosed secret in the pipeline industry that PPR plastic pipe is not suitable for domestic tap water pipe, because PPR raw materials are cheap, easy to install and the profits are considerable.

5. Copper tubes

Copper tubes and their accessories are complete in variety and specifications, with a large diameter range, and can be selected from 6mm to 273mm at will. Copper pipes are easy to bend, process and change shape, which can meet all the requirements of pipeline wiring and interconnection in engineering installation. Especially in the field construction, the temporary cutting, bending and grinding of copper pipes are easy. All kinds of pipes and fittings can be assembled and delivered to the site, or temporarily installed on the site, with satisfactory results.

copper is a hard metal and corrodes. Can be used in different environments without damage. Judging from the service history of foreign countries, the service life of many copper pipes has exceeded the service life of the building itself. Therefore, copper water pipes are absolutely safe and reliable.

copper can be said to be a "red metal with a green face". Copper can inhibit the growth of bacteria and keep drinking water clean and hygienic. Copper tableware has a long history and is non-toxic and tasteless.

copper pipes and fittings can still maintain their shape and strength under high temperature and high pressure, and there will be no long-term aging phenomenon.

The copper tube has a dense and hard protective layer, so that no matter oil, carbohydrate, bacteria and viruses, harmful liquids, air or ultraviolet rays can pass through it or corrode it and pollute the water. Parasites can't live on copper surfaces either. But the high price of copper pipe is its biggest shortcoming, and it is the most advanced water pipe at present.

6. Composite pipes

With the continuous development of industry and technical improvement in China, a large number of new materials and new processes have been adopted in water supply and drainage projects, and composite pipes have been widely used in building water supply projects.

(1) aluminum-plastic composite pipe

The middle layer of aluminum-plastic composite pipe is made of welded aluminum pipe, and the outer layer and inner layer are made of medium-density or high-density polyethylene plastic or crosslinked high-density polyethylene, which are bonded and compounded by hot melt adhesive. The pipeline has both the pressure resistance of metal pipeline and the corrosion resistance of plastic pipeline, and is an ideal pipe for building water supply. Aluminum-plastic composite pipe generally adopts threaded clamping sleeve for pressure welding, and its fittings are generally copper products. First, the fitting nut is sleeved on the pipe end, then the inner core of the fitting is sleeved in the end, and then the fitting and nut can be tightened with a wrench. Good high temperature resistance, convenient construction and greatly improved labor efficiency. Long-term thermal expansion and cold contraction of pipeline will cause dislocation of pipe wall and leakage. Aluminum-plastic pipes are easy to burst when pressed. In areas where the decoration concept is relatively new, aluminum-plastic pipes have gradually lost the market and belong to eliminated products.

(2) Steel-plastic composite pipeline

Steel-plastic composite pipeline is a composite pipe with a certain thickness of plastic lining (coating) on the inner wall of steel pipe. Generally divided into plastic-lined steel pipes and plastic-coated steel pipes. Steel-plastic composite pipes are generally connected by threads, and their accessories are generally steel-plastic products.

7. Thin-walled stainless steel pipes

With the development of national economy and the improvement of people's living standards, thin-walled stainless steel pipes and stainless steel pipe fittings have become a new trend in the development of domestic water supply pipeline systems. Thin-walled stainless steel pipes that meet health requirements will not cause secondary pollution to water quality, and meet the needs of national direct drinking water quality standards.

Thin-walled stainless steel pipe is a kind of water pipe that can be completely recycled, and it won't leave any garbage that can't be treated for future generations.

The strength of thin-walled stainless steel pipe material is higher than that of all water pipe materials, which greatly reduces the possibility of water leakage caused by external forces and saves a lot of water resources.

Thin-walled stainless steel pipe has excellent corrosion resistance, no scaling during long-term use, smooth inner wall, low transportation energy consumption and cost saving, so it is the lowest transportation cost water pipe material.

the thermal insulation performance of thin-walled stainless steel pipe is 24 times that of copper pipe, which greatly saves geothermal energy loss in hot water transportation.

Thin-walled stainless steel pipes will not pollute high-grade sanitary ware, thus avoiding "red marks" and "blue marks" that cannot be scrubbed on sanitary ware.

At present, in the field of thin-walled stainless steel water supply pipes and fittings, the main difference between related similar products is the different connection methods, so the following is the most common and convenient thin wall.

the connection mode of stainless steel water supply pipes and fittings-clamping connection. Connecting pipes with socket fittings with sealing rings, and pressing the nozzle with special tools for sealing and fastening. The basic composition of clamping pipe fittings is a special-shaped pipe joint with O-ring in the U-shaped groove at the end. When assembling. Insert the stainless steel water pipe into the pipe fitting, and seal it with a special sealing tool. The pipe fitting and pipe in the sealing part are extruded into a hexagon, thus forming sufficient connection strength, and at the same time, the sealing effect is generated due to the compression deformation of the sealing ring. The cost of pipe fittings is low, which is suitable for popularization in the civil market. The open-faced installation project is simple and the construction speed is fast.

8. Water supply cast iron pipes

Water supply cast iron pipes have the advantages of strong corrosion resistance, convenient assembly, long service life (generally, the service life of underground cast iron pipes is more than 61 years), low price, etc. They are mostly used in water supply pipes with DN greater than or equal to 75 coffee, especially suitable for underground laying. Its disadvantages are brittleness, large mass, small length and worse strength than steel pipe. There are three kinds of straight water supply cast iron pipes produced in China: low pressure, normal pressure and high pressure.

In recent years, in large-scale high-rise buildings, ductile iron pipes are designed as general risers and applied to indoor water supply systems. Ductile iron pipe has thinner wall and higher strength than ordinary cast iron pipe, and its impact performance is more than 11 times that of gray cast iron pipe. Ductile iron pipe adopts rubber ring mechanical interface or socket interface, and can also be connected by threaded flange.