Before heading out on vacation, most of us run through a familiar checklist—turn down the thermostat, toss anything questionable from the fridge, water the plants, and secure doors and windows. Yet one surprisingly common culprit behind that stale “nobody’s been here” smell often gets ignored: the bathroom or kitchen sink. When a home sits empty, the plumbing system isn’t active, and the drain can quietly become a source of odor and dampness.

Under every sink sits a curved pipe called a P-trap, designed to hold a small pool of water. That water works as a protective seal, blocking sewer gases and tiny pests from drifting upward into your living space. Daily handwashing, dishwashing, and general use normally replenish this water. But if you’re gone for several days or weeks, it can slowly evaporate—leaving the drain exposed and your house vulnerable to musty, sour smells.

There’s an easy, cost-free way to prevent this: place a dry paper towel over the drain opening and gently cover it with an upside-down drinking glass. The paper towel acts as a breathable barrier, controlling odors and discouraging insects, while the glass keeps it securely in place without trapping moisture. Unlike rubber plugs, which can warp or loosen over time, a glass stays put and doesn’t disrupt airflow.

For best results, give the sink a quick refresh before leaving. Rinse it with hot water, pour in a splash of white vinegar to break down residue, and wipe the basin dry. Then set the towel-and-glass in position, lock up, and enjoy your trip. When you return, your home will welcome you with the same clean, fresh scent you left behind—proof that a simple minute-long habit can make a surprisingly big difference.