"Pin hole" corrosion of inner water pipes

[e573]

Who can explane, why the inner water pipes in building became "pin-holed"?
May it be due the AC electrical current flow on this pipes or exist another reasons?
What must be done in this situation?

Thanks in advance.

 

[snafuman]

could be the chemical makeup of the water. Don't know alot about this, but believe their is a "blue water" (common name) test the run on water, after is has been sitting in copper pipes (assuming you have copper pipe) all night. The tests shows whether is copper is leaching into the water. You may want to check this out with a testing lab.

 

[CTSSA]

If the material of construction is steel, pin-hole corrosion is usually due to high chlorides in the water source. If the material of construction is a yellow metal alloy leachate can occur, the area around the pin-hole developes a characteristic spongy appearance.

 

[AEF]

Depends on the material of construction, but mainly its due to trace elements corroding preferentially in the metal. An example are pin hole leaks in 3XX series stainless steel tubes in steam/water heat exchangers. Manganese sulfide inclusions on the metal surface, exposed to the electrolyte, form weak polythionic acids that corrode the inclusion to metal boundary. The reaction continues into the metal forming very narrow, deep pits. Same type of thing occurs in 'dirty' copper tubing. Your best bet is to replace the material with plastic tubing.
Stray electrical currents can also have an effect on corrosion, but not normally in residential applications. More limited to cathodically protected underground systems.

 

The causes of pinhole leaks are numerous and some of the most common causes are: water quality characteristics, pipe manufacture, pipe installation, ... and possibly stray currents. The actual causes are very difficult to pin down, and it is often a combination of the various reasons which lead to problems. The utility which I work for has been investigating pinhole leaks (causes and how to prevent) for the past 12 months, due to a high number of pinhole leaks in our distribution system.

I highly recommend you review the book entitled "Internal Corrosion of Water Distribution Systems" by AWWA Research Foundation, 1996; this is an EXCELLENT source of information whether your problem is copper, cast iron, ... This reference has photos of the various examples, history, causes, and preventive methods / recommendations. Check out the book - you won't regret it. Also, there are several paperback AWWA Research Foundation reports on more specialized topics.

 

[ripple143]

I have a pinhole leak in a steel water jacket. However, production will not allow me the down time i need to drain the tank and fix it from the inside. Any ideas?

 

[GarySCWSVI]

Galvanic Cells are another corrosion causer. Dissimilar metals contacting in the plumbing. Usually galvanized iron connected to copper.

Gary Schreiber, CWS VI
The Purolite Co.