1. The production of drinking water.
The drinking water treating factory will treat the raw water through a series of processes, to make it achieve the health standard for drinking water, and then lead it into water supply system for the end-users to use.

The water that enters the water treating factory is called raw water, raw water has different sources, including ground water like well water and spring water, surface water like river water, lake water and reservoir water. No matter ground water or surface water, they all contain minerals, metals, chloride, and also contain bacteria and solid impurities (organism and mineral). The ground water commonly has lower oxygen content, and sometimes will contain hydrogen sulfide, reduction sulfite, bacteria, etc.
The raw water requires treatment before it can achieve drinking water standards; the raw water entering the factory is commonly treated with oxidability chemical objects like chlorine and potassium permanganate, to generate the iron and manganese into hydrate to deposit, and these deposit will hurt the pipe wall, in order to eliminate these deposits, flocculate and other particles; in the process of neutralizing the water and deposit the metal ions, particles, activated carbon or detritus/ gravel will be used to carry ultimate filtration, then the water after ultimate filtration will be disinfected by chlorine or hypochlorite. After the series of treating process, the production of clean drinking water achieving the health standards and with low iron, manganese content is completed. These clean water will be supplied to the end-users through the water supply system.

The above production processes show, that in the series of treating processes, the impurities in the water and the chemical substances added, will cause various corrosions to the treating equipments. Practice shows, in the medium environment of water treating process, corrosion will occur to the treating equipments. Commonly, the life span of cast iron, steel and copper alloy is only 20-40 years, and limitation should be given to the water flow speed, chemical components of water. By comparison, stainless steel can have a service life of more than 100 years with no limitation to water flow speed and chemical components of water, thus stainless steel is widely used in water treating, water supply system, reservoir pool and water tank, apart from increasing the life span of the treating equipments, the sanitation conditions of stainless steel equipments are much better than those with other materials.

2. The application of stainless steel in production equipments of drinking water.
The production equipments of drinking water are mainly made of 0Cr18Ni9 and 0Cr17Ni12Mo2; the former is fit for water with 200ppm chloride content, while the latter is fit for water with 1,000ppm chloride content, in low temperature drinking water; it is seldom seen that 0Cr18Ni9 will have part corrosions like the corrosion pitting, crevice corrosion, etc.; the main reason for choosing 0Cr17Ni12Mo2 is to prevent corrosion problems caused by outside environment. In water treatment, more severe corrosive environment might be met, at this point, choose 22%Cr and 25%Cr double phase stainless steel with high strength and resistance to corrosion pitting and stress corrosion. The super austenite stainless steel containing 6% of Mo, like 254SMO、654SMO etc, is mainly used to make the nozzle for jetting chemical drugs.

In the water treating factory, water supply system and indoor water pipes, the metallurgy products that use stainless steel include stainless steel welded pipe, pipe joints, flange, valve and fastening piece, etc. The actual application status is shown in the following Table 1 and Table 2.

Table 1 - The application of stainless steel in water treating factory

Name of part and equipment	Material
Water pool scaleboard, filter, inlet components, slide door, river weir	0Cr18Ni9
Filtration web, paddle, fastening piece, pipe, air tube, pipes for sample fetching sensor	0Cr18Ni9
Pipes for chemical drug treating, reservoir pool paddle, platform, gap bridge, cover plate	0Cr18Ni9
Activated type tower, ozonizer and pipes, rail, pump, valve	0Cr18Ni9
Nozzle for chemical drugs	6%Mo Austenite stainless steel

Table 2 - The actual application of stainless steel in water supply system

Application position	Material	Remark
The main pipe and horizontal pipe of new water supply tunnel, No.3 Manhattan Island, America	0Cr18Ni9，φ1,200mm, all welded pipes 300m	100 years of life span
New butterfly valve for water supply, No.3 Manhattan Island, America	0Cr18Ni9，18 φ1200mm ,Welded pipes and casting butterfly valves	100 years of life span
Repairing the underground water supply pipe (channel less distribution), Turin, Italy	0Cr18Ni9，φ550X1500mm welded pipe
Water supply pipes with span of 10-480 meters, Japan	0Cr17Ni12Mo2，φ100-170mm welded pipe
Water supply pipe with span of 10-480 meters, small pipe bridge at the seashore area, Japan Japan, water supply stand pipe buried underground	25% Cr double phase stainless steel（SUS329J2L）φ100-170mm welded pipe ，φ750-1200mm welded pipe ，Mo2 double phase stainless steel welded pipe
Underground water supply pipe, Kalskoga City, Swiss	0Cr17Ni12，22% thin sheet lining
Cross mountain water supply tunnel （φ3,600m）, North Italy,	0Cr18Ni9，0.6mm thin sheet lining	No leakage after 6 years of usage
Connecting pipe between water supply pipe/ secondary line and the water meter of the customers, Japan	0Cr17Ni12Mo2，φ75-350 welded pipe ，φ50mm, indoor welded pipe
Reservoir pool, Matsuyama, Japan	0Cr18Ni9，0Cr17Ni12Mo2 liquid phase SUS329 double phase steel
Village water tower, Sweden	0Cr17Ni12Mo2