Before leaving home for vacation, many people place an upside-down glass over their kitchen sink drain with a piece of paper underneath. The trick has become popular online because it supposedly keeps sewer odors and insects from entering the house. However, the glass and paper do not create an airtight seal, meaning they may provide little real protection. The actual issue is hidden inside the plumbing, where water in the sink’s P-trap can slowly disappear while the home is empty.

Every sink has a curved pipe called a P-trap that holds water and blocks sewer gases and insects from traveling into the house. During a long vacation, that water can eventually evaporate, and once the trap dries out, unpleasant smells and insects may enter through the drain. The viral glass trick does not stop this process, but there is a much easier solution that takes only a few minutes.

Before leaving, run water through every sink, shower, and bathtub for about 10 to 20 seconds. Flush the toilets and check less-used drains in places such as basements and laundry rooms, since these can dry out more quickly. For longer trips, properly fitted rubber or silicone drain covers can provide a better barrier, while built-in stoppers can help reduce evaporation.

For vacations lasting several weeks, homeowners can take additional precautions. A small amount of mineral oil added to a filled drain trap can slow evaporation, while shutting off the main water supply may reduce the risk of certain leaks. The most effective solutions aren’t exciting, but refilling your drain traps and using proper covers can help prevent unpleasant surprises when you return home.