About 20 years ago we were experiencing pin hole leaks. Our plumber thought it was because originally the house was on well water. Rather than deal with each leak one at a time, we eventually had him do an extensive repipe of the house. All was well until this year - one of the pipes (luckily exposed) in our basement has had two pinhole leaks in the past few months. The leaks were not at joints.

So a couple of questions:

  1. Is the theory about well water being the cause reasonable?

  2. At the time I believe the plumber also said this type of problem would be less of an issue with hot water pipes, but the leaks this year were in a hot water pipe. Is that true? If so, could it just be a "bad" pipe?


  • I assume these are copper pipes? My daughter has had the same problem in her house, built in the mid 60's, with copper pipes. But I do not know the thickness of the walls in the pipes (Type L, M?). Some of it has been replaced with PEX.
    – SteveSh
    Jul 23, 2020 at 0:58
  • Yes, this particular one is copper - should have mentioned that. PEX had been used to replace other pipes. Jul 23, 2020 at 1:15

2 Answers 2


High mineral counts can be a problem, not having proper dielectric unions and my opinion CHEAP pipe. I have seen cheap pipe have 50 pinholes where the rest of the house was fine the funny thing we could still see the stamps on the pipes and it was the cheap brand that had all the leaks. Replaced those sections and 10 years later the rest of the pipes are still fine, just the thinner cheap copper was the problem.


Strangely enough both very high PH and very low PH water can each cause corrosion in copper pipes resulting in pinhole leaks. Turbulence in pipes caused by too many 90 degree elbows is also considered to be a causative factor. As Ed mentions the situation is exacerbated when cheap (thin) copper pipes are installed.
I'm not ready to get 100% behind PEX yet - not enough history there to date. However, my suggestion is:

  1. If you're seeing extremes in PH levels, sometimes caused by high mineral content, install a water conditioner.
  2. If you are having copper pipe installed don't go cheap with it - you'll pay down the road.
  • +1 I agree, and will add: at some point (I am thinking late '80s) the market was flooded with cheap substandard copper pipe made in Mexico (both Type-L & M) that is causing pinhole leak trouble still today. Also, back in the day there was no requirement to ream/deburr cut copper pipe (as there is now) and this can cause erosion downstream due to turbulence/swirl. Jul 23, 2020 at 2:55

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