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odd plumbing problem

boag's picture

The other morning I came into the kitchen and found it covered in water dripping from the ceiling. After removing the ceiling I found a pinhole leak in the 3/4" copper pipe.  I shut off the water and started to think about how to fix it (in a totally inaccessable location). About a day latter - while still thinking- I new leak ocurred in an totally different location of the house. Same type of leak.

I removed the entire run of piped in the second location (easily accessabe and looked at it). A small pinhole - no bulging etc. The plumbing has in for 25 years the wall thickeness looked good.


Has anyone run into to this before?



High pH water with chorine (post #204026, reply #1 of 12)

High pH water with chorine initiated byproducts. 

Greatly accelerated if the Cu pipe carries any leakage electrical current which increases rate of electrolysis.  Multiple grounding of electrical circuits to the Cu pipe can do it - e.g. the basic power ground and a ground added in a different location to the Cu pipe for cable or other reasons. 

Laying against an aluminum support wire for a dropped ceiling or aluminum flex conduit is an even greater accelerator, but you would notice that when you found the leak.

Own house is 40 YO and zero corrosion on well water. Mom's house im midwest on muny water system is 103 YO and no Cu pipe problems ever.  

thanks for the reply - both (post #204026, reply #2 of 12)

thanks for the reply - both leaks were in the middle of  a run with no dissimiliar metals near. ????

It's a very commom problem (post #204026, reply #4 of 12)

It's a very commom problem here in south Florida to the point that there are plumbers who do nothing but repipe houses plumbed with copper. They typically use CPVC and charge from $3 to $4,000 including drywall repair but no  paint.

Florida Licensed Building Contractor, 50 years experience in commercial remodeling, new homes, home remodeling and repairs and all types building maintenance.

It was my understanding that (post #204026, reply #3 of 12)

It was my understanding that it was acidic water that causes copper corrosion -- low pH.  IIRC, areas of Florida have lots of trouble with this.

Of all the preposterous assumptions of humanity over humanity, nothing exceeds most of the criticisms made on the habits of the poor by the well-housed, well-warmed, and well-fed.  --Herman Melville

Get the water tested. You (post #204026, reply #5 of 12)

Get the water tested. You could just take it to a swimming pool place and get most of the basic tests for free. They will tell you about chlorine content, pH, total disolved solids, total alkalinity and a few other things you don't really care about.

Good "city" water should test about like good pool water. If your TDS is low (less than 100 or so) or your pH is much below 7.2, that may be eating your pipes. City water chlorine is usually 2.0 or so.

When they were having this problem across the river in Cape Coral, they were blaming it on Reverse Osmosis water not having enough disolved solids. That was just one excuse though. There were also questions about how the electrical system was grounded.


Pinhole corrosion. (post #204026, reply #6 of 12)

Easy answer without all the math:

Most likely cause is that the city has cast iron mains, and little bits of iron are getting into your system. 

They then lie on the botom of lines that don't have much flow velocity, and cause a galvanic corrosion cell.  The copper disolves to electroplate the iron that is in contact with it, leaving a pinhole in the copper pipe. 

Not only do we have iron (post #204026, reply #7 of 12)

Not only do we have iron mains, the water is saturated with iron when it comes out of the well.  But copper pipe holds up just fine around here (except for a peculiar circumstance at the gym where I go, involving stagnant soft hot water in a stub pipe).

Of all the preposterous assumptions of humanity over humanity, nothing exceeds most of the criticisms made on the habits of the poor by the well-housed, well-warmed, and well-fed.  --Herman Melville

Iron in solution isn't an issue: (post #204026, reply #8 of 12)

Iron particles are an issue.  If the mains are old enough to have chancer, and little bits of the rust particles are spalling off and being transported by the flow, they can get into the house. 

If they get into a line and stay in one place they will form a corrosion cell.  Which then forms the pinhole. 

I've been out of town and am (post #204026, reply #9 of 12)

I've been out of town and am able to give the final results.

While looking at the original leak a second one developed in the basement. I thought about the issue with iron in the line but this line is the main line into to the house 3/4' and heavy flow (no time to settle) the original leak was in the main line leading to the upper floors (same situation).

I replaced all the original lines in the basement over the weekend and had to leave - my wife called in a plumber and had him fix the upper line (everything was cut and he was able to replace the line an an hour).

In looking at the leaking line they are true pin holes - no thinning of the walls, clean with no sediment.

The major cause for pinhole (post #204026, reply #10 of 12)

The major cause for pinhole leaks in copper pipes is low pH. If the pH of the water is lower than 5.5, it is harmful to copper.  Please check the pH of the water. Adding an acid neutralizer to the existing equipment seems to be a good option.

cause of pinhole leak (post #204026, reply #11 of 12)

Pinhole leaks occur when corrosion inside copper pipes finally breaks through to the outside of the pipe.

The reason why copper pipes leak is due to turbulence.

Fittings that are too close together increase turbulence, which causes pinhole leaks. When fittings are too close together, turbulence in the water flow increases, which means the water grates against the inside wall of the pipe causing it to leak


Lenora R Walton

Troll and BS call. Pinholes (post #204026, reply #12 of 12)

Troll and BS call.

Pinholes from turbulence in residential Cu pipe?  BS.  

How about showing a calculation of the Reyolds number in 1/2 Cu pipe with a 6 GPM flow thru say 5 interconnected elbows? Then relate that to the internal stresses on the copper.  Shoul CU pipe elbows be stellite lined <G> 

Always willing to learn something...