I have a sprinkler system (i.e. irrigation system) at home. Occasionally I park my car too close and it gets hit with the water. This causes horrible water spots. I've seen that some do-it-yourself car washes have a "spot free rinse", that is to say water that does not cause water spots. I assume they use some sort of filter. Is it possible to add such a filter to my system? Where would I get it? How would I install it? Does anyone know a good way to remove water spots from a car?
Conditioning all the water to your irrigation system is probably not the right approach. For one thing, it's expensive, and for another, the conditioners might hurt the plants.
More frequent car washes might be--a good coat of wax can help the water slide right off, rather than sticking and then drying in place. If you're that concerned about car appearance it's probably worth going to a place that does good solid waxing.
You might also ask this in the Mechanics site.