Do you have a reverse-osmosis (RO) system or use water softener?

Free of minerals and salts, a reverse osmosis (RO) system's water is graywater-friendly (just send the RO concentrate to the sewer).

If you have a water softener, consider using a potassium-based water softener instead of sodium-based, bypassing the clothes washer from the softened water, adding a reverse-osmosis system, or trying alternatives to conventional ion-exchange water softeners [PDF and study evaluating water-softener alternatives].

Salt, or sodium chloride, is commonly used in water softeners to remove the hardness from water in homes and businesses.
Potassium chloride works exactly the same way that sodium does in the water-softening process. However, there has been a slow but steady growth in the use of potassium chloride (KCl), which is chemically related to salt and has the same water-softening characteristics.
Most water softeners remove hardness (calcium and magnesium) and iron from water through an ion-exchange process. The harder the water, the more sodium or potassium respectively is added to effect softening.

Potassium chloride is a naturally occurring mineral, and it is often marketed as agricultural plant food.
Sodium can be harmful to plants, whereas potassium is an essential mineral for plant growth.
By switching from sodium chloride to potassium chloride, it will reduce sodium and chloride being discharged into municipal wastewater treatment facilities, thus enhancing the quality of recycled water and soil conditions.

If you switch from using salt to potassium chloride, you may just add the potassium chloride pellets into the tank where salts are added.
No equipment changes or adjustments are required for most household water softeners; however, please refer to your owner’s manual or contact manufacturers for compatibility.
Also, please consult your physician if you have any health-related questions about consuming potassium chloride-treated soft water.