"Hidden engineering" is a very important issue. If the water pipe leaks and bursts, it will bring irreparable consequences.
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. However, after a few years of use, it is easy to produce a large amount of rust, breed bacteria, and seriously endanger human health. The state has stipulated that sand mold casting pipe fittings and cold-dip galvanized cast iron pipes shall 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, new plastic pipes, etc.
The state also stipulates that all kinds of pipes and fittings involving drinking water pipelines must be approved by the health department before they can be sold.