Piping Material

I think we need more information.
Normally 2" (50mm) would be the largest size you would need to use. Unless of course you are making your own drinking water.

Is this a drinking water processing or treatment plant?

Where is your project located?

You can construct your piping system from a galvanized steel up to NPS 4" to be threaded connected. But you can fabricate your piping system from a larger standard up to NPS 4" of CS material, to be connected by welding, furnished with flanges, and to be hot dip galvanized HDG after completion of fabrication. The piping system can be assembled together by connecting and tightening the flanges wih gaskets.

It is prohibited to weld carbon steel after galvanizing due to the toxic fumes from melting of galvanized steel, and also to avoid the rusting of that weld during operation.

Can you use PVC? I've seen that used for potable water lines at 175 mm OD.

Good morning sachin rastogi. Is your pipeline above or underground?

Why not procure GI PIPE from pipe mill ?

Yes, Mr. Sachin first let me tell you that galvanizing is possible above 2"size also, with extra arrangement which increases the cost of production.

Secondly, whether your requirement is only for drinking water above/under ground line and for safety showers inside the operatinal plants like fertilizers,refineries,petrochemical etc., you need not require more than 2" size even for laying of a drinking water header, & it can be 2" and below to save the cost & time of construction.On the other hand whydon't you go for PVC material whereever is possible, which is comparatively cheep and good also.You will get good quality of PVC material in the market.

PVC and PE are very popular.