Galvanized pipe is generally not recommended for underground applications. In addition to the corrosion issues, you also have a potential problem with the threaded joints. Underground potable water piping generally uses flexible joints that compensate for for soil movements.
ok for what?
it will rust, is that ok?
what pressure?
what fluid?
soil resistivity?
water table depth?
amount of rain?
design life?
pipe wall thickness?
type of coating?
Your questions are about piping design.but I am not talking about that.imagine the pipe is correctly selected according to your questions.is it acceptable for underground galvanized pipe to be seal welded?
Does not it cause to galvanic corrosion?
of course it corrodes, all ferrous metals corrode whether they are galvanized or not. most galvanized is screwed pipe so I cant comment on your welding procedures. but likely does not increase the corrosion resistance.
your post directly relates to design and desired design life. galvanized iron is not typically used underground, welded or non welded. doesn't mean it cant be done if the conditions warrant. if your soil is not highly corrosive and your pressure is low and you select a thick pipe, properly coated and wrapped and you have a 5-year design life, than go ahead and use galvanized iron - it might be acceptable. if you have corrosive soil, high water table, high pressure gas service, 100-year design life, than use something else.
Screwed galvanized pipe was used extensively in residential and commercial real estate irrigation and potable water lines. Depending on soil conditions and stray currents, life spans over thirty years were obtained - or less than 5 years! We now use PVC/HPVC plastic pipe.
Seal welding of galvanized pipe destroys the corrosion resistance of the galvanized pipe at the welding points. It is probably not a good idea. It also makes the piping a restrained joint system also not a good idea for underground pipe. Fumes from seal welding of galvanized pipe is probably hazardous to the person installing the weld.
I have heard of some significant use of galvanized steel pipe for even drinking water service, particularly in Third-World areas. This is probably due to the fact that it is known capable of being hauled in, assembled with semi-skilled labor, and physically deliver most of the water at reasonable cost and for at least some time holding up in demanding exposed and/or partially exposed environments to physical damage as well as e.g. rather unrelenting tropical sun etc. However, e.g. in virtually all the United States now e.g. all materials coming into contact with potable water must be NSF 61 listed as being suitable for that contact, and I'm not exactly sure how many manufacturers are promoting this certification (notice also the current guidance under the heading, "Benefit of Material to Systems Application" at
My community has many galvanized steel water service lines, much to the owner's regret. We now specify HDPE (or copper, for those with money to spare).
