easier said then done, especially if you dont have a garden of course.. and/or if you dont live in particularly wet part of the world.. but setting up a small rain collection tank in your yard seems like a pretty simple idea, maybe uneffective or unreliable.. but better than tap water.. Im from wales, and I have no idea whats in the water main, I know theres small amount of fluoride & copper... I would like to get a reverse osmosis machine but they look expensive... but there are alternative such as basic 'Brita' Water Filters, they are pretty cheap and a worthwhile investment.. It not just what the effect of giving impure water to your plants is, your nutrients are also effected when feeding your plants.. they tend to lose effectivity, or even react.. Copper Fluoride Nirtrogen Phosphorus Potassium.. sounds like a mad experiment.