jaygreg wrote:

For some time now, I've watched mineral deposits slow the flow of water
in selected pipes. Plain household vinegar does an excellent job of
dissolving it... if your can get the vinegar to the metal. Many years
ago I used it in my water take and all turned out well...

I live in Arizona and have very hard water. Steel pipes clog up fast
and eventually develop pinholes, sometimes in just a few years.
Copper pipes build up a layer of calcium that stays thin and doesn't
have to be removed. The pipes also last forever (I live in a home
with 60-year-old copper pipes). Plastic pipes develop an even
thinner layer of calcium, and PVC and CPVC lasts forever, provided
it's covered from sunlight and no gophers chew through it.