Your softener needs to “regenerate” every few days. That means it flushes out the nasty minerals. You need a drain hose for that.
Run a small hose from the softener’s drain port to a floor drain, a laundry tub, or a dedicated pipe. Use a standpipe if you can, but a simple drain works too.
Salt Water Softener System Diagram Water Softeners Why? Service
Make sure the hose is lower than the softener. Gravity is your lazy assistant here. Don’t make it climb uphill—water hates climbing.