Very interesting. I recently found out the house I grew up in in the UK over 15+ years had lead pipes that were never replaced, and I always wondered why they were not replaced and if it had some cognitive impact. This lining effect likely explains the reason, and offers at least some reassurance.

If the water PH changes, the value in replacing those pipes might become more apparent.

I wonder how did you figure out this is the case, did you make any tests of the water?

I can hardly imagine living in a house with lead pipes. I mean even if water if provably safe today, what if tomorrow PH shifts to acidity.