Is watering with well water a good idea?

@ Mark...The easiest way to manage water with high ppm's, is lower the total ppm's of your feed, and work your way up from there. I also do a run off test every once in a while to check the substrate ph and ppm . After a while you will learn how far you can push the plants with ferts. 

depends on alot of things! Texasbob has your best answer. the well water is only going to be as good as the environment that surrounds it. Just like some people swear by "rain-water"...  The rain water in Los Angeles and larger more industrialized cities is going to be loaded with all the chemicals floating around in the environment. 

If you live in nice farmland away from the industrialization and smog and heavy traffic it might be good. I used to use tap water in my DWC until my city started getting fucky with their treatment. now i only trust distilled because its a blank canvas.

@ Invi, what's the ph of the well water ?

What do you lower the ph with, and what's the ph of your final fert solution goin in ?

Bloom city ph down, going in is about 5.4-5.7 coming out is about 6-6.5 when is 6.5 i do 5.4 going in