Galvanize and Potable Water
Galvanize and Potable Water
(OP)
Hello,
I would like to ask that potable water affects to galvanized piping negatively.
If yes, what is the reason. Which material in galvanized pipe is affected by potable water?
Thanks
I would like to ask that potable water affects to galvanized piping negatively.
If yes, what is the reason. Which material in galvanized pipe is affected by potable water?
Thanks





RE: Galvanize and Potable Water
It is typically at the threaded/mechanical fittings where this issue occurs because the galvanic layer gets scratched/abraded/etc. during installation.
RE: Galvanize and Potable Water
RE: Galvanize and Potable Water
RE: Galvanize and Potable Water
I used to count sand. Now I don't count at all.
RE: Galvanize and Potable Water
Dead wrong on that. In fact the opposite is true: a galvanizing coating is superior BECAUSE it provides at least some anodic protection to the underlying steel pipe in areas where the coating is damaged, like it is at every cut thread or rolled Victaulic groove in the pipe.
That said, galvanized pipe isn't a long term solution in potable water because there is a continual source of fresh oxygen in that water. Eventually the zinc will corrode away and leave the steel underneath unprotected. But it will STILL be superior to ungalvanized steel in terms of survival.
In treated cooling water or closed loop cooling systems, galvanized will last a very long time, and the galvanic joints matter much less.
Where galvanized pipe fails prematurely is typically at unmanaged galvanic joints. When people thread brass or bronze valves into galvanized pipe, or make threaded transitions to copper lines using brass fittings, galvanized pipe fails rapidly. Any attempt at galvanic isolation at these joints needs to avoid being short-circuited by pipe supports and ground wires. And no, teflon tape provides no useful galvanic isolation in a typical NPT joint!
Copper and plastics (PEX, CPVC) are better choices, though copper can corrode quite quickly in some potable waters- it depends on the pH and mineralization of the water.
RE: Galvanize and Potable Water
The zinc is an anode and provides cathodic protection.
Steve Jones
Corrosion Management Consultant
http://www.linkedin.com/pub/8/83b/b04
All answers are personal opinions only and are in no way connected with any employer.
RE: Galvanize and Potable Water
Remember even distilled water can be corrosive!
RE: Galvanize and Potable Water
RE: Galvanize and Potable Water
I would tend to agree but I have seen studies which indicate localized corrosion of galvanized pipe. While these studies are for fire suppression dry systems, the underlying theme is similar, I.e. impinged zinc coating and replenished oxygen in the water.
http://ecscorrosion.com/wp-content/uploads/2013/09...
http://corrview.com/rokdownloads/cfp_01.pdf
Some have even stated that galvanized pipe is worse than black steel for these systems. I haven't accepted this yet, but it is of interest.
I haven't yet stopped specifying galvanized pipe in fire suppression, but would not specify it for domestic uses. On remodels, I typically have it removed and replaced.
RE: Galvanize and Potable Water
I can believe that the zinc in some services may not be worth its cost- but have great difficulty believing that the zinc is of no use at all or worse than using bare steel pipe. That makes no sense to me at all. If nothing else, the zinc provides external corrosion protection at a cost far lower than painting small-bore pipe, which is the primary reason we use it for most of our Category D piping.
Thanks for the correction SJones- I'm forever messing up anodes and cathodes, anodic and cathodic, anions and cations...