Please offer any info if you've installed a tankless heater system in the past year or so. Have you had any problem with calcium buildup? Have you any experience with <http://easywater.com> saltless soft water maker?
I have six tankless water heaters for the past 3.5 years. Only soft water goes through them and I have not had any buildup as there is nothing to build up.
I know of someone who used a product similar to the "Easy Water" device - he ended up replacing his boiler because the tubes became completely plugged with calcium, and the lack of flow caused some of the tubes to buckle and burst.