A simple vacation tip has been making the rounds online, claiming that placing a sheet of paper over your sink drain and covering it with an upside-down glass before leaving home can keep sewer odors and insects from entering your house. The trick has attracted plenty of attention, but does it actually work? While the idea is rooted in real plumbing principles, the viral method itself isn’t the most effective solution.
The reason this hack exists is because of a plumbing component known as the **P-trap**. Located beneath sinks, bathtubs, showers, and many floor drains, this curved pipe is designed to hold a small amount of water at all times. That water creates a protective seal that blocks unpleasant sewer gases and helps prevent insects from traveling into your home through the drainage system.
Problems begin only when that water evaporates. If a drain goes unused for a long period, the water inside the P-trap can slowly disappear, breaking the seal. Once that happens, foul odors—and in some cases insects—may find a path into your home. This is why people who travel for extended periods sometimes return to unpleasant smells coming from rarely used drains.
Fortunately, this isn’t something most homeowners need to worry about during a weekend getaway or even a typical one- or two-week vacation. Under normal conditions, the water trapped inside the P-trap usually lasts several weeks before evaporation becomes an issue.
However, certain conditions can cause the water to disappear more quickly. Homes located in hot, dry climates, areas with strong airflow, or rooms that rarely receive water—such as guest bathrooms, basement floor drains, or laundry standpipes—are more likely to experience dried-out traps sooner than expected.
The viral paper-and-glass trick is based on a reasonable theory. Covering a drain could reduce evaporation and provide an additional barrier if the water seal eventually disappears. In principle, limiting airflow over the drain makes sense.
The problem lies in how the hack is performed. Simply placing a sheet of paper over the drain and resting an upside-down drinking glass on top doesn’t create an airtight seal. Without a tight fit, air, odors, and even insects may still find their way through. The paper can also become damp from humidity, wrinkle, or shift out of place, making the setup even less effective. A small bump to the sink could easily move everything aside.
Instead of relying on a viral internet trick, there are much more dependable ways to prepare your plumbing before leaving town.
The first and most important step is refreshing every P-trap in your home. Before you leave, run water in each sink, shower, bathtub, and floor drain for about 10 to 20 seconds. Flush every toilet once as well. This simple step restores the protective water seal inside every drain.
If you’ll be away for an extended period, it’s also a good idea to cover your drains properly. Close built-in drain stoppers where available, or use rubber drain plugs or silicone drain covers that fit tightly. If nothing else is available, plastic wrap secured over the drain opening or painter’s tape can serve as a temporary barrier.
For even greater protection during long trips, many experienced plumbers recommend adding a small amount of mineral oil after running water into the drain. About one tablespoon is enough. The oil floats on top of the water, slowing evaporation and helping the water seal remain effective for much longer. It’s important to use mineral oil rather than cooking oil, which can spoil or contribute to plumbing problems.
A few additional precautions can also make returning home much more pleasant. Empty all trash cans, clean the garbage disposal to eliminate lingering food odors, and, if you’re traveling during freezing weather, ensure exposed pipes are properly insulated. Some homeowners also choose to shut off the home’s main water supply before leaving, reducing the risk of leaks or burst pipes while the house is empty.
The popular online hack simplifies a real plumbing concern but doesn’t provide a dependable solution. While the idea of covering a drain has some logic behind it, a loose piece of paper and an upside-down glass won’t reliably protect your home.
The best approach is much simpler and far more effective: refill every P-trap with fresh water, seal drain openings using proper covers or plugs, and, for longer vacations, consider adding a small layer of mineral oil. These practical steps will do far more to prevent sewer odors and unwanted pests than any balancing-glass trick circulating on social media.