Kits come with the sump basin, sewer ejector pump, check-valve. The waster line is run into the sump basin, pumped through a checkvalve into the sewer line that grades with gravity. If you add a high water alarm, which is a good idea. The check valve makes sure, that what you pump out, stays out. Otherwise the pump will keep cycling.
Plumbing codes call for a gap between potable water and a drain.
Sometimes it is a hose left in a mud puddle, or maybe a hose lying in bleach water. People have died this way. The plumbing code helps protect the general public from these dangers. A. Several things could happen. First check the shower head volume if shower's are too quick.