When people prepare to go on vacation, they usually think of locking doors, unplugging electronics, and cleaning out the fridge — but one often-overlooked concern is the sink drain. If a sink isn’t used for some time, especially over long absences, the water that normally sits in the P-trap (the U-shaped section of pipe under the sink) can evaporate. That water forms a seal that prevents sewer gases and pests from entering your home; when it disappears, that protection is gone, leaving your house vulnerable to smells and infestation.
This drying-out effect is particularly acute during hot weather or periods of no use. Without regular water flow, the P-trap’s seal breaks, allowing foul odors — often described as rotten-egg or sulfur-like — to seep up through the drain. It’s not just about smell: plumbing experts warn that dry traps can also open a pathway for insects and even rodents to crawl into your home. Bugs like drain flies, cockroaches, spiders, and silverfish may exploit the gap, and, in extreme cases, small animals have been known to navigate plumbing systems.
Fortunately, there are simple, low-cost preventative measures. One effective method endorsed by many plumbers involves running water in seldom-used drains at least once a month — this refills the trap and reestablishes the water barrier. For even longer-lasting protection, experts recommend adding a little mineral oil on top of the water in the trap. Because the oil floats, it slows the water’s evaporation, helping maintain the seal much longer.
In addition to keeping the trap full, routine cleaning helps ward off odor-causing buildup. Organic matter like soap scum, hair, grease, and food particles can cling to the walls of pipes and form biofilm — a slimy, bacterial layer that produces unpleasant gases as it breaks down. To clean it, many recommend pouring a mix of baking soda and white vinegar down the drain, letting it fizz for a while, and then following with hot water.
If you’re about to leave for vacation and want to take additional precautions, here’s a quick prep routine: thoroughly clean the sink and drain, then pour in hot white vinegar or the baking soda-vinegar mix. Let it sit for some time, rinse with warm water, and optionally rub a lemon wedge around the drain to leave a fresh scent. Finally, refill the P-trap with water, top it off with a small amount of mineral oil to prevent evaporation, and seal the opening (some suggest using a cap or stopper).
For an extra barrier, especially when you’re gone for a while, you can also cover the drain opening with a damp paper towel and place an inverted glass over it. As noted by recent expert advice, this makeshift seal slows evaporation better than many drain stoppers, which can deform in heat or lose their tightness. This “glass and towel” trick not only helps preserve the water seal but also physically blocks insects from crawling up.
By taking these small but effective steps before you leave, you can avoid returning to a home filled with musty smells or worse — insect invaders. Maintaining even a trickle of water in the trap, adding mineral oil, and sealing the opening ensures the P-trap stays functional. Rather than walking in to unpleasant surprises, you’ll come back to a fresher, safer space — and one less thing to worry about while you’re away.
