Seeing more pinhole leaks in copper lately?

I only ran into this issue 1 time about 20 years ago at my boss's house. . He had a bathroom located over the garage and the garage had a drywall ceiling. The pin holes were always in the cold-water line…never the hot. All 1/2" L copper.

You would fix one leak then 6 months later another leak would pop up. I blamed it on flux residue as the Copper Development Assn says how hot water will flush out the leftover flux where cold water will not.

I have seen corrosion on copper pipes on the outside where "Utility" brand flux was used and probably was never washed off. For that reason, I always use "Nokorode" flux which I never had issues with.

The erosion happens just down stream of the edge.

I suspect most plumbers dont take the time to analyze the cause of the pin holes. Blame it on cheap pipe, flux, the previous plumber,etc.

Hot water recirc is most common erosion corrosion, hot water moving too fast. I have seen it more in commercial buildings where plumbers think they need a big pump for a big building.

I used to have a collection of these. Copper scrap prices became too tempting to hoard them.

I have never seen a copper pex insert fitting pinhol;e. Ideally you would not have many fittings in a pex recirc loop, maybe two in the mech room?

But not all pex handles hot, chlorinated constant recirc conditions.

You want a pex with the "5" in the listing number.