fredrosse wrote:OK, so the problem with "galvanized pipe" is not that it has zinc coating, but that usually it is lower quality pipe, although so is the typical steel pipe you get at the discount supply stores.
I'm going to have to say that I'm not sure what the whole story is. I know that class 3000 (3000 psi @ 72f) pipe is available as galvanized and is claimed to be suitable for steam service. The standards cross reference is something that I need to look into further. Maybe there are some issues with galvanic corrosion when zinc is present in some cases or there is another reason that makes it unsuitable.
My gut tells me that since there are no clear references that galvanized pipe is acceptable for boiler external piping that one should not use it. The references that I have come across generally say that galvanized pipe is unacceptable but it appears that it's due to the choice of DIY quality pipe not specifically the zinc.
Not sure why the prohibition for power boilers, but it is also prohibited for any sort of propane or natural gas transfer. Reason there is because the galvanize coating can come loose - flow down the pipe and cause a valve to malfunction. I would speculate that is the same reason it is not allowed on power boilers and piping. A flake of that under the seat of a relief valve would prevent it from closing.
Not sure why the prohibition for power boilers, but it is also prohibited for any sort of propane or natural gas transfer. Reason there is because the galvanize coating can come loose - flow down the pipe and cause a valve to malfunction. I would speculate that is the same reason it is not allowed on power boilers and piping. A flake of that under the seat of a relief valve would prevent it from closing.
-Ron
Ahyep. That's how the Oregon State boiler inspoection folks explained it to me 15 years ago.
Ahyep. That's how the Oregon State boiler inspoection folks explained it to me 15 years ago.