FWIW:
I just paid over $200 for a complete lab eval of our stick-house well water because of possible affects from the CA drought. The results showed it's water (less of it, however, due to the drought) was about the same chemical comp as it was 25 years ago.
It reads between 750 and 800 on my TDS meter and a pH of around 8.5. We've been using it in the house for cooking, clothes washing, and showers for years this way with no effect on our (copper) plumbing. We do not drink it. The iron in it never makes it to our house because the weekly manual chlorination I do within our 5000 gal storage tank is converting the iron into a chemical composition such that it settles out right there in the tank and doesn't even get to our home's parallel 1 micron whole-house filters. These filters (coconut shell carbon block) take out the chlorine taste/odor that would normally be present from the chlorine that I put in ahead of them down at the storage tank, so the disenfected water from the tank carries no free chlorine when we use it in the house.
Even though our well water has a whole bunch of minerals in it, it's only twice as heavy in TD solids as some city waters - many of which read 300-400 on TDS meters. Water disinfection is the important thing - not necessarily disolved solids content. Our well water actually feels very soft and pleasant for showering because of it's high TDS readings.
We recently added 10,000 more gallons of water storage into our system and will be paying for trucked-in water to fill them until the well output (hopefully) increases this winter.
Now back to fresh water purity as it relates to our RV ... we use this under-sink filter in the galley in addition to trying to never put water into the RV's fresh water tank that hasn't been disinfected:
http://www.discountfilterstore.com/water-filter-commercial-everpure-ev9592-06-adc.html?gclid=CMClvOfqh8ACFehaMgodFG0AEA