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Galvanized steel water pipe
3

Galvanized steel water pipe

Galvanized steel water pipe

(OP)
I am using a 14" diameter galvanized steel pipe for potable water design. The pipe is exposed and hanging from the concrete bridge overhang. The pipe line is approximately 600 linear foot and water pressure inside of the pipe is 250 psi. The job requires that the pipe to be made in USA. I do not know if this type of pipe stick has a bell at the end or they just just weld it in the field. I am looking for the cut sheets for the pipe but have problem locating a pipe manufacturer/supplier in northern California. I can use schedule 40, 80 or 120. Appreciate any input.

RE: Galvanized steel water pipe

At 14 inch and 250 psi I think you have exceeded the ratings of common field assembled systems such as grooved piping meaning you'll need welded flanges. In this case, I suggest buying uncoated pipe, welding the flanges, and then shipping out for galvanizing. No welding will be done in the field as it damages the coating. 14 inch pipe is available in 60 foot sections but requires a special mill run (we used it for pilings), 21 feet is standard otherwise. I don't know about galvanizing such long lengths. Galvanizing is done by the pound and is relatively inexpensive. There are vendors in northern CA that specialize in acquiring USA made pipe (look near shipyards) and there is also an outfit that can perform hot dip galvanizing not far from that same vendor.

RE: Galvanized steel water pipe

2
During the decades-spanning between the 1930s and 1960s, galvanized steel was the material of choice for water distribution lines inside buildings. It no longer is. The problem with galvanized pipe is that it is subject to corrosion internally and at the joints.

Why don't you recommend ductile iron pipe with mechanical joints?

RE: Galvanized steel water pipe

Have you thought about a steel line internally lined with a thin PE pipe?

But 14"is a strange size and at 600 ft may not be stocked. Try 16" or 12" is my suggestion.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

RE: Galvanized steel water pipe

I would not used galvanized steel for potable water.

Ductile iron, as bimr mentioned, is probably the most common pipe type for this application. Based on my experience, the pipe would be cement mortar lined and either painted or epoxy coated. You could also put this pipe inside a steel casing and push it through on skids. I have done this before, but with the regular (and thin) black coating the pipe came with instead of paint or epoxy.

LittleInch: 14" is a common size for water pipe, although I don't see as much of it as I used to.

============
"Is it the only lesson of history that mankind is unteachable?"
--Winston S. Churchill

RE: Galvanized steel water pipe

I would suggest API 5L pipe with polyethylene exterior coating and a plastic liner that will satisfy your local potable water rules. If you weld galvanized pipe ,you burn off the zinc near the weld. You could use thread and coupled galvanized to satisfy the legal requirement but I would say that is a very poor engineering choice.

RE: Galvanized steel water pipe

Don't forget that corrosion happens on both sides of the pipe and threading removes the galvanized coating from the outside of the pipe where you will also lose the galvanic protection effects due to open air.

RE: Galvanized steel water pipe

I have seen some rigid joint pipe hung under and alongside bridges, mostly flanged (~4" to ~20"), with some threaded (<= 4") and some welded (~4" to ~12"). However, the more flexible the bridge and the larger the temperature swings, the more important it is to have flexible joints, at least in part, which ductile iron pipe can certainly provide.

============
"Is it the only lesson of history that mankind is unteachable?"
--Winston S. Churchill

RE: Galvanized steel water pipe

Ductile iron pipe is commonly used for municipal water systems. API 5L seamless and welded steel pipe is commonly used for the transportation of petroleum and natural gas.

As fel3 mentions, ductile iron pipe can be supplied with mechanical joints to allow joint flexibility. That is an advantage that API 5L pipe doesn't have.

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