Most water softeners use salts to bind with the metals in the water and make the water “soft.” This kind of water is not suitable to be reused outside as it is high in salt and can harm plants and soil. Alternatives to sodium water softeners are potassium softeners. Depending on the level of hardness and the way the water softener system is set up, some people are able to bypass their washing machine from the softener and then reuse that portion of their greywater. There are other options for softening water, such as magnets. We have no personal experience with magnets, and would like to hear from anyone who uses them.