Nope, the Britta filter use a combination mesh/activated carbon system to remove some impurities but they do not remove hardness.
Originally Posted by Shmoo
If you want to remove hardness you need a water softening system that uses ion exchange resins, these system, by their nature also filter grit, etc, etc.
Since I worked in the industrial water purification industry, I was lucky to have all the deionized water I wanted. Since I moved to Mexico, that is no longer an option, heck, they dont even sell distilled water here, dont know what it is. So I started using drinking water from bottles and that has worked fine. The specs for drinking water are good enough for film developing, you dont need deionized or distilled water.