Common building water supply and drainage pipes are mainly plastic pipes, metal pipes and composite pipes. But in fact, there are far more than these categories, and there are more new types of pipes.

1. Steel Pipes

(1) Introduction

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

(2) Connection

  Threaded connection is to connect with threaded pipe fittings. Most fittings are made of malleable cast iron, which are divided into galvanized and non-galvanized types, and have greater corrosion resistance and mechanical strength. Galvanized steel pipes must be connected with threads, and their fittings should also be galvanized fittings. This method is mostly used for exposed pipes.

  Welding is to connect two sections of pipes together by welding with a welding machine and welding rods. The advantages are tight joints, no water leakage, no accessories, and   fast construction. But it cannot be disassembled. Welding is only suitable for non-galvanized steel pipes. This method is mostly used for concealed pipes.

  Flange connection is often welded (or threaded) to the pipe end on a larger diameter (more than 50m) pipe, and then the two flanges are connected together with bolts, and then the two sections of the pipe are connected together. Flange connection is generally used to connect valves, check valves, water meters, water pumps, etc., as well as pipe sections that need to be frequently disassembled and repaired.

2. Plastic water pipe

  For water supply rigid polyvinyl chloride pipe (UPVc), the temperature of the delivered water shall not exceed 45℃. UPVC pipes are generally connected by sockets and spigots, of which socket bonding is suitable for pipes with an outer diameter of 20 to 1601m; rubber ring connection is suitable for pipes with an outer diameter greater than or equal to 63mm; and connections with metal pipe fittings, valves, etc. are made by threaded or flanged connections.

  For water supply polypropylene pipes (PP pipes), it is suitable for system working pressures not exceeding 0.6Mpa and working temperatures not exceeding 70℃. Water supply polypropylene pipes are connected by hot-melt sockets and spigots. When connecting with metal pipe fittings, polypropylene pipe fittings with metal inserts are used as transitions. The pipe fittings are connected to the polypropylene pipe by hot-melt sockets and to the metal pipe fittings by threads.

3. PVC pipe

  Plastic pipe, the joints are usually glued. It has poor frost and heat resistance, and the pipe is easy to break and deform when heated. It is suitable for electrical wiring pipes and drainage pipes.

4. Copper pipe

  The diameter range is large, and can be selected from 6mm to 273mm. The pipe is easy to bend, easy to process, and easy to change shape, which can meet all the needs of pipeline wiring and interconnection in engineering installation.

  Copper is a hard metal, but it corrodes easily. It can be used in different environments without damage.

  Copper pipes and accessories can still maintain their shape and strength under high temperature and high pressure, and will not age for a long time.

  Copper pipes have a dense and hard protective layer. No matter grease, carbohydrates, bacteria and viruses, harmful liquids, air or ultraviolet rays can penetrate it or erode it to pollute the water quality. But the high price of copper pipes is its biggest disadvantage. It is currently the most high-end water pipe.

5. Composite material pipes

(1) Aluminum-plastic composite pipes

  The middle layer of the aluminum-plastic composite pipe is welded aluminum pipe, and the outer and inner layers are made of medium-density or high-density polyethylene plastic or cross-linked high-density polyethylene, which are bonded and composited by hot-melt adhesive.

It has the pressure resistance of metal pipes and the corrosion resistance of plastic pipes. It's an ideal pipe for building water supply.

It's generally crimped by threaded ferrules, and its accessories are generally copper products. Due to long-term thermal expansion and contraction, the pipe wall will be misaligned, resulting in leakage. In areas where the decoration concept is relatively new, aluminum-plastic pipes have gradually lost their market.

(2) Steel-plastic composite pipes

  They're made by lining (coating) a certain thickness of plastic composite on the inner wall of a steel pipe. Generally, they are divided into two types: plastic-lined steel pipes and plastic-coated steel pipes. Steel-plastic composite pipes are generally connected by threads.

6. Thin-walled stainless steel pipe

A water pipe that can be fully recycled, usually with a press-fit connection.

The thermal insulation performance is 24 times that of copper pipes, saving a lot of geothermal energy loss in hot water transportation.

7. Water supply cast iron pipe

  Water supply cast iron pipe has the advantages of strong corrosion resistance, convenient connection and installation, long service life (generally, the service life of underground cast iron pipe is more than 60 years), low price, etc. It is mostly used in water supply pipes with DN greater than or equal to 75 mm, especially suitable for underground laying. Its disadvantages are brittleness, large mass, small length, and poor strength compared with steel pipe. There are three types of water supply cast iron straight pipes produced in my country: low pressure, general pressure, and high pressure.

8.UPVC pipe

It's the most consumed variety among all kinds of plastic pipes.

Main features:

1. Good chemical corrosion resistance, no rust.

2. Smooth inner wall, fluid conveying capacity is 43.7% higher than cast iron pipe.

3. Low price.

4. Light weight, easy to expand, bond, bend and weld.

Main application areas: building water supply and drainage pipe system, building rainwater system.