In the past, the pipes used for water supply were mainly cast-iron pipes. Sand mold cast iron pipes are mainly used outdoors and galvanized cast iron pipes are used indoors, which can be divided into cold (electric) galvanizing and hot galvanizing. My country has stipulated that sand mold casting steel pipe fittings and cold galvanized cast iron pipes should be eliminated from June 1, 2000, gradually restrict the use of hot-dip galvanized cast iron pipes, and promote the use of aluminum-plastic composite pipes and plastic pipes. Therefore, there are three main types of pipelines currently in use. The first category is metal pipes, such as plastic-lined hot-dip cast iron pipes, steel pipes, stainless steel pipes, etc. The second category is plastic-clad metal pipes, such as plastic-clad steel pipes and aluminum-plastic composite pipes. The third category is plastic pipes, such as PP-R (cross-linked polypropylene high-density network engineering plastics).


The state also stipulates that all kinds of steel pipes fittings involving drinking water pipelines must be approved by the health department before they can be sold. Commonly used plastic codes and meanings in water supply pipelines:
　　PP—R cross-linked polypropylene high-density network engineering plastic
　　PE high-density polyethylene
　　PP polypropylene
　　PB Polybutene
PEX cross-linked polyethylene

Comprehensive performance requirements of water supply pipelines:
As a water supply pipeline, sanitation, safety, energy-saving, and convenience are required. Therefore, the inspection of a pipeline should start in four aspects. Namely sanitation: the steel pipes fittings must not result in any harm to the human body. Safety: It has sufficient strength and excellent mechanical properties, as well as anti-aging and heat-resistant properties. Energy-saving: smooth inner wall, corrosion resistance, low resistance to fluid, and good heat preservation performance. Convenience: It is convenient and reliable to connect and construction, and has the possibility of popularization.
If the above four requirements are not met, the user's health and property safety will be damaged.