What is causing pin-holes in my cold water lines?

[three_jeeps]

House was built in mid 60s. Original copper pipe throughout. Over last 5-6 years, been chasing pinhole leaks in cold water lines in the unfinished basement, once in a riser to 2nd floor. Typical mid-60s split level suburban house, AFAICT, type M used throughout, 1/2". Strange that it has only happened on cold lines. Water is on the hard side. I talked to some neighbors in the plan (about 15 houses, all built by some company), a few (3-4) have seen this problem. Talked to people one street over, one house has similar issues.

I am at the point where I am going to replace all the cold lines in the basement with new copper, and will us L. Will probably go up to 3/4" for more volume, and will probably put in expansion tank.

The bottom line question is, What is the cause of the pin holes?
One plumber suggested installing a water softener but was just guessing. A few ppl suggested that it is something the township is putting into the water (scary thought).
Another data point, all the sink, bath, and toilet shutoffs are useless - either frozen or bottom out without stopping the water. I've replaced about half of them with 1/4 turn ball valves.
I know the old shutoffs dont work after a while, but seeing this at all the fixtures makes me wonder.
Thanks for any insight.
J

 

[Twowaxhack]

Your pipe is 60 years old. Combination of wear, water ph and possibly some electrolysis.

Any 1 of those 3 or a combination of the 3.

water quality and composition can change over time......especially from a well, not that you have a well.

60 years isn’t a bad run..... I’ve seen it last 3 years and some last for 80++++++

Plumbing requires maintenance that very few are willing to take the time to do or are willing to pay for. Nothing lasts forever. Your pipe was for sure undersized, this can cause pinholes(wear/erosion)

 

[Jeff Handy]

What about corrosion from too much flux in soldered fittings?

On hot lines, the excess flux softens and gets carried away.

Cold lines, it can cling to the pipe wall and cause pitting.

 

[Twowaxhack]

What about corrosion from too much flux in soldered fittings?

On hot lines, the excess flux softens and gets carried away.

Cold lines, it can cling to the pipe wall and cause pitting.

Actually it happens on both hot and cold lines. Flux corrosion is real snd it usually happens at the bottom of a header assembly.
Main cause is using too much flux to make up fir not cleaning the fitting very well. This flux runs down the pipe when the header is being soldered up.

Her pipe was undersized. From what she’s posted Id go with that if I had to pick a cause. Under sizing causes higher velocity that causes wear.

 

[three_jeeps]

Your pipe is 60 years old. Combination of wear, water ph and possibly some electrolysis.

Any 1 of those 3 or a combination of the 3.

water quality and composition can change over time......especially from a well, not that you have a well.

60 years isn’t a bad run..... I’ve seen it last 3 years and some last for 80++++++

Plumbing requires maintenance that very few are willing to take the time to do or are willing to pay for. Nothing lasts forever. Your pipe was for sure undersized, this can cause pinholes(wear/erosion)

Thanks...I gave this a bit more thought.., did a quick n dirty flow measurement did some math...given 1/2" pipe, the flow at a faucet would be turbulent. so flow erosion is a definite possibility.
I never considered that copper pipe would 'wear out' but it is possible.
I seem to remember reading some time ago, that long time ago (40s? 50s?), that pitting of copper pipe occurred and the metallurgical properties of the pipe was changed to avoid this. I am assuming that the pipe in my house is 'newer' and would not have that problem.