I'd argue this was a foolish way to do it. For example, when they put in a water system into our basement, they routed the effluent from a softener and two filters into our sump crock. No problem that I saw at the time. After all, they must know what they are doing. A few months later the sump pump died from the salt and other crap periodically being dumped into the crock.
I replaced the pump, but not before I ran the effluent from the backwashes into the outflow line after the pump. No problems now, since the pump never sees any backwash water. And since the backwash effluent comes out under pressure, there was never any need to pump it up out of the basement anyway.
John