Check Valve in Kitchen Sink Drain Pipe

[Jvstevens]

I encountered a pretty slow kitchen sink drain today, so I decided to remove the trap for cleaning, and to gain better access to snaking the drain downstream, if needed. The drain pipe (1.5" ABS) went through the right side wall of the sink cabinet and into an unused volume of the adjacent corner cabinet. I noticed that there was an access panel cut in the side of the sink cabinet, so I removed the two screws holding it in place to have a look inside. It seems someone added an inline 1.5" sump pump check valve (per the label still on it), presumably to prevent backflow into the sink. I had never seen something like that in a kitchen drainpipe before, so I wasn't sure if this was a standard practice or some desperate attempt to solve a backflow issue. Anyway, I took the check valve off and cleaned a lot of accumulated "gunk" inside of it, which I theorize was jamming up the flap/hinge mechanism and causing the slow drain. I also cleaned out the trap, etc and snaked a few feet of pipe downstream from where the check valve was. I reinstalled the check valve and everything else, then tested it all out. Drains nice and fast now, so problem solved.

So, my question is, is installing a check valve (specifically, a sump pump check valve) in a kitchen sink drain line an acceptable practice? This all happened in a 1st floor condo kitchen (of a 3 story condo), so I'm guessing there have been past problems of ground level drain clogs causing backups into the 1st floor kitchen sink when 2nd and 3rd story residents use their sinks, but perhaps there is another explanation? Would it be wise (or unwise) to remove it?