Installing water softener - rinse drain location question

[gregobru]

I'm planning on installing a water softener, but the water into the house isn't in an ideal location for the drain. It's on an exterior wall adjacent to the master bathroom. Laundry, hot water, kitchen (etc) are on the opposite side of the house (concrete slab).

Short of running the drain tube into the attic, across the house, and down into the laundry standpipe, the only solution I can think of is to run it though the exterior wall into the master bath and to drain it into the plumbing beneath a bathroom sink.

So long as I install an air gap, is this going to be a problem? Are there any notable concerns here?