This is my first post so please forgive me if I commit a faux pas.
We have city sewer and a sump pump for gray water. A neighbor informed us that we should not have the water softener overflow draining into the city sewer system. When we put it into the sump pump an employee at the hardware store said the water could damage the seals on the sump pump and to put it back.
Hello and welcome Nancy to the best darn DIY'r site on the web.
I have had a softener flushing into my sump for more than 10 years with no ill effect to the pump. The small amount of water which flushes through the media tank on a softener will be well diluted when discharged into the sump so I wouldn't worry about it.
When its all said and done there is usually more said than done