Question:
I have installed 50 meters of 25mm galvanized steel pipe over seven years ago. Yesterday I noticed a rust spot appearing on the outside of this pipe, with water leaking from the rusted spot. This suggests that the pipe is rusted from the inside towards the outside. I have noticed many more rusted areas. This pipe hangs in th ceiling. Could someone please tell me the reason for this problem.
Anwser:
This usually occurs when the water chemistry is on the acidic side (low pH). It eats out the softer areas of the steel pipe and eventually makes a pinhole leak that will grow bigger in time. The hole is actually larger inside the pipe than the outside. kind of like a volcano shape.
If it is one or two holes they can be patched by covering the hole with a piece of rubbery material held in place with a hose clamp. When the holes get to be too many or too large, then it is time to replace the pipe. This is odd that it is doing it to galvanized pipe. Either the pipe was poor quality to begin with or your water is really bad.
If the situation is caused by bad water chemistry, then it will occur again if you use copper pipes as a replacement. The best way to go is to either use PVC if allowed by code in your area, or get out the check book and get 316 stainless steel pipes and fittings.
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