The Black Berkey filter elements are designed to remove heavy metals, but will not remove mineral salts added by a water softener. This is because a water softener adds mineral salts to water to make it softer. The salt used to soften water is not extracted by a Black Berkey filter element and even causes the element to clog. You can still use a Berkey water filter if it is possible to bypass the water softener. Most water softeners have a bypass valve or a way to get water before it passes through the softener. Therefore, we strongly recommend using that water instead of running softened water through your Black Berkey filter elements.