I'm selling my house, and the home inspector pointed out that the
kitchen drain is not vented, so the new owner (hopefully!) wants that
fixed. Isn't there a way to do that with a check-valve, or some such
easy solution??

It's been working for me for the last 4 years (despite the occasional
gurgle), and don't think it's been any different since construction in
1980... I sure don't want to do a major remodeling just to make this
sale.

Thanks,
DP