A popular travel tip circulating on social media suggests placing a sheet of paper over your sink drain and covering it with an upside-down drinking glass before leaving for vacation. Supporters claim this simple trick prevents unpleasant sewer odors and insects from entering your home while you’re away.

While the concern behind the advice is legitimate, plumbing experts say the paper-and-glass method isn’t the most effective solution.

Why Drains Can Smell After You’ve Been Away

Every sink, bathtub, and floor drain contains a curved pipe known as a P-trap. This U-shaped section always holds a small amount of water, creating a barrier that prevents sewer gases, unpleasant odors, and pests from traveling up through the plumbing and into your home.

If a drain goes unused for an extended period, the water inside the P-trap can gradually evaporate. Once that protective barrier disappears, foul smells and, in some cases, insects may be able to enter through the drain.

Does the Glass-and-Paper Trick Actually Work?

Although the idea has become popular online, it has several drawbacks.

Paper towels or tissues can become damp, tear apart, and even fall into the drain, potentially contributing to clogs. Meanwhile, simply placing a drinking glass upside down over the drain doesn’t create a complete airtight seal, allowing odors to escape through small gaps around the rim.

The glass can also be accidentally moved while you’re preparing to leave, making the method even less reliable.

Better Ways to Protect Your Drains

If you’ll be away from home for several weeks, there are safer and more dependable options.

Mineral oil: Pour a small amount of mineral oil (or baby oil) into rarely used drains. Because oil floats on top of the water in the P-trap, it slows evaporation and helps preserve the water seal for a longer period.

Plastic wrap: After drying the area around the drain, cover it tightly with plastic wrap. This creates a temporary barrier that can help reduce odors and discourage insects from entering.

Rubber drain stopper: A standard drain stopper is another simple solution. While it may not create a perfect seal, it helps slow evaporation and provides an extra layer of protection.

When Should You Be Concerned?

For most people, there’s no need to worry if you’re leaving for only a few days or even a week. Under normal conditions, the water inside a P-trap usually remains in place for several weeks.

You may want to take extra precautions if:

You’ll be away for three weeks or longer.
Your home is located in a very hot or dry climate.
You’re protecting drains that are rarely used, such as those in guest bathrooms, basements, or laundry rooms.
The Bottom Line

The viral upside-down glass trick isn’t necessarily harmful, but it isn’t the most dependable way to protect your home while you’re away. Understanding how your plumbing works—and using proven methods like mineral oil, plastic wrap, or a drain stopper—can help keep your home free of unpleasant odors and unwanted pests until you return.