I think I know where the leak was but can't repair it due to corrosion. 

It simply is a corrosive chemical that crawls to wiring and pipe, just like mold did.

No need to replace the water lines unless they show signs of significant corrosion and are leaking. 

I've replaced so many of these over the years & it can be an easy job if the pipe runs are accessible or a nightmare if you need to go through walls.The last one was a MF that had a mixture of Galv & 3/8 water Cu lines connected without any catalytic protection so the joints all had severe galvanic corrosion & were leaking.

The water heater had a little corrosion, which I saw (and frankly means it needs to be replaced) and he said one previous inspector noticed a little condensation in the electric panel.

He found that the cast iron under the basement has some corrosion and would probably need to be replaced as another blockage would probably happen.

Some of the breakers have old rust and minor corrosion, as well as some of the wire ends.

It is non-corrosive to concrete and tends to be effective over a longer duration.

They just put a bandaid on each time until the condenser coils needed replaced due to corrosion but they tried to say it could be cleaned which was my responsibility, they were out at least once a year. 

I heard a leak and after some detective work and cutting open the back of my kitchen cabinet I finally have located a few pin holes at the bottom of a kitchen copper drain line.These pin holes unfortunately are impossible to patch in that the cause is corrosion and is almost always caused by tenants or previous owners sending hazardous chemicals like Draino down the line and those chemical sat at the bottom and ate at the line and eventually you get holes.