The answer to 'water softener rusty water' is that a rusty water issue after installing a water softener is usually caused by the softener's iron-removing capabilities being overwhelmed or not functioning properly. This can lead to iron buildup in the plumbing system, resulting in reddish-brown or orange-tinted water.
Common causes include an undersized softener, a softener that needs regeneration, or a problem with the softener's iron-removal media. Symptoms may include stained laundry, plumbing fixtures, and appliances. Solutions can involve adjusting the softener's settings, replacing the resin, or upgrading to a larger capacity softener. In some cases, a professional plumber may need to inspect the system and make repairs.