Wellhouse - Water Filter
Available for about $50 from:
http://www.filtersfast.com/OmniFilter-U25-whole-house-water-filter.asp
The connection is for 3/4 inch pipe.
The best filter cartridges to use are the TO1 type and they cost about $9 from:
http://www.filtersfast.com/OmniFilter-TO1-T01-water-filter.asp
http://www.omni-water-filters.com/cartto1.htm
A couple of times a year you may need a new O ring. It's the OK25. They cost about $5
http://www.filtersfast.com/OmniFilter-OK25-water-filter-o-ring.asp
http://www.omni-water-filters.com/cartto1.htm
Another possibility is to use a Reverse Osmosis Water Filter.