Pin hole leaks from high pressure?

[FullySprinklered]

Earlier in the day I read something in a post that but a bug in my ear. Jadnashua responded to someone, saying that high pressure in the water lines could cause a decrease in the lifespan of the water pipes.

So, let me throw this out there. His assessment of the situation jives with some of the things I've run into out there.

I fixed a pin-hole leak in a copper pipe a couple of days ago. Easy fix with a couple of Sharkbites and some PEX pipe. The pipe I removed was maybe two feet long and the pinhole leak was somewhere in the middle.

When you look down the pipe there's always this scab on the inside exactly where the pipe is leaking on the outside. On this pipe there were half a dozen scabs in a straight line on the inside of the pipe.

Can I assume that this line of scabs is following the line where the pipe was originally pressed together as sheet metal when it was rolled into tube. I know quite well that frozen copper pipes split in a perfectly straight line and I've always assumed that it was along the line where the tube was formed from sheet.

Now, is this line where the pipe was swaged together a potential line of weakness if the pressure within the pipe repeatedly exceeds what's allowed?

Thanks for any input;

Oh, by the way, There's been a few times where the customer had pinhole leaks also had bad pressure issues: PRV and ET replacement.

 

[Kreemoweet]

https://www.copper.org/publications/newsletters/innovations/1998/09/howdo_tube.html

Copper tube not made from sheet, therefore no "seam" to act as a locus of weakness. I can't think of how pressure itself could cause
deterioration, except as it would lead to high flow velocities. Fluid turbulence and cavitation in
flowing water is a well-known cause of metal "corrosion", pitting, and ultimate failure.

 

[Sponsor]

 

[FullySprinklered]

I'll reread the production process as time allows. Looks like they have a process that makes for a perfectly homogenous tubular product. Then why does frozen pipe have a perfectly straight longitudinal split? Want pictures?

 

[PumpMd]

You can also have low PH from your water to cause pin hole leaks as well. If, this is the case, expect more pin hole leaks in the future.

 

[FullySprinklered]

Oh, hell. Thought I'd made some kind of monumental discovery. Never mind.

 

[PumpMd]

I said "if" that is the case. PH can be tested

I think that would leave only one other explanation for your findings.

 

[Bluebinky]

Just a wild guess, but maybe because the initial ice will tend to float to the top of a horizontal pipe and then grow downward...

 

[Atomic1]

If you can post a few photos, I might be able to deduce what the failure mechanism is. (background in material engineering and failure analysis) The split could be a secondary effect of pressure exploiting a thinned area of material.

FWIW, the Ph of groundwater in my region is about 7 and I still hear about folks getting pinholes. Therefore, wouldn't be surprised if it was something other than acid erosion.

 

[FullySprinklered]

What really set me off is the piece of tubing that I removed in order to resection the pipe with Pex fittings and pipe.
Always, when you look down the pipe there will be a lump/scab/bump on the inside of the pipe where the leak occurred.
This time I noticed quite a few bumps inside the pipe, all in a straight line. That seems to say something. The bumps were not randomly scattered about. I can't say for sure about the orientation of the line of weakness, but on past jobs the leaks seem to occur equally on the top, bottom, or side of the pipe. I wish I'd paid closer attention, but my main concern has been to repair the pipe.

 

[Jadnashua]

One thing that can cause problems is if, when you cut your pipe with a tubing cutter, you do not take the time to reform the end so that it is straight...the tubing cutter tends to make a slight flare in the end. That can cause turbulence (cavitation), and at a certain flow rate (the higher the flow rate, the stronger the cavitation), you can get 'waves' that can repeat along the length downstream of a fitting that progressively get dampened the further away from the problem.

There are a bunch of 'rules' when putting together a system that, if you do not understand the whys involved, you dismiss, and, under some circumstances, can come back to bite you in the butt. Usually, they don't happen immediately, which can make for a disconnect on the cause and effect.

It's possible that you could get that from an older joint when they were still using acid based flux, or, you could have a defect in the pipe itself.

 

[Valveman]

It has been a few years but I had part of my house re-modeled and they put in new 1/2" copper. Within 3 years I had two pin hole leaks. My plumber replaced it with some Pex. He said every house he plumbed at the same time they did my house had the same problems. Apparently they got some bad copper pipe and had a lot of trouble with it.

 

[Jadnashua]

The thing to look at is the distance from a joint. If those holes are in a long section of pipe without fittings, it's probably a defect in the pipe or contamination. If they're within a foot or two downstream of a fitting, it's more likely the plumber did not reform the end of the cut pipe, and it had cavitation, and eroded from within. The higher the flow, (higher pressure can allow increased flow) the more likely you can get this sort of problem. It's more common on undersized piping, as that requires faster flow. This usually takes awhile to show up...

 

[Valveman]

My problem was in the middle of a 20' long piece of 1/2" copper. At least 5' from any connection.

 

[Jadnashua]

Most common pipe lengths are 10', although longer ones are available. A connection doesn't have to be an elbow...it could be just an inline coupler. But, full-length sections wouldn't have the deformation from a tubing cutter at their ends, but it's not uncommon for it to get a bit damaged during transport. That leaves potential pipe defects as the most likely culprit. Cavitation, over time, can erode lots of things.

 

[FullySprinklered]

I often find that if I have trouble figuring out a problem it's because there's more than one problem. All of the above may contribute something to the original issue: pinhole leaks. There's an epidemic of copper leaks in my part of the world, so I'm looking for something definitive to blame it on. The workaday solution is to go fix the leaks regardless of cause, but I can't help but wonder.

 

[Jadnashua]

Some water supplies are just corrosive, and will damage copper piping. There are some places where the only long-term solution is some sort of plastic pipe. Often, though, it's the soil, but those pipes aren't buried. If a public water supply, you should be able to get a copy of the water analysis for free from them.

 

[Terry]

I just replaced some 1/2" copper pipe in an attic that had seveal leaks. The weepy pinhole stuff.
My neighbor had on in his crawl space a few years back. It happens every so often I get a call like that. It make me wonder when we will be repiping all the homes I plumbed with copper.