I'm thinking of putting an accessible powder room off a kitchen/livingroom space. I vaguely remember that there has to be two doors between toilets and kitchens, is that correct?
No. What is needed is a threshold at the door that is above the level of the tile, and sanitary base or tile wainscoting installed. You want to keep water inside the bathroom. That includes the toilet backing up or sewage backup. It won't stop it for long but gives you a window of about 5 to 10 minutes to do something about it.
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