The upside-down glass looked almost reassuring.
There it was, sitting neatly over the sink drain with a small sheet of paper underneath it. It was the kind of simple household trick that sounded clever enough to believe. Maybe your mother did it before a family vacation. Maybe your grandmother swore by it. Cover the drain, place a glass upside down over it, and supposedly you could leave home knowing that unpleasant smells and unwanted little visitors would stay where they belonged.
For years, people have passed along tricks like this because they seem to make sense. You're leaving your house empty for days or even weeks, so covering the drain feels like an obvious precaution. Nobody wants to come home after a relaxing trip, open the front door, and immediately notice that unmistakable sewer smell. And the thought of drain flies, cockroaches, or other pests finding their way through unused plumbing is enough to make anyone want to cover every drain in the house.
The interesting part is that the concern behind the trick is real. Drains can become a source of unpleasant odors when a home has been sitting unused for a long time. But the upside-down glass isn't really addressing the most important part of the problem. The thing protecting your home isn't sitting on top of the drain. It's hidden underneath it.
If you've ever looked beneath your kitchen or bathroom sink, you've probably noticed a curved section of pipe shaped somewhat like the letter P. That's the P-trap. It isn't shaped that way by accident. A small amount of water remains inside the bend after you use the sink, creating a barrier between the air in your home and the plumbing system beyond it. Under normal conditions, that little pocket of water quietly does its job without you ever thinking about it.
Problems can begin when a drain isn't used for a long period. Water sitting inside the trap can gradually evaporate, particularly in warm or dry conditions. If enough of it disappears, the water barrier that normally separates your living space from the drainage system is weakened or lost. That's when unpleasant odors can become noticeable, and certain insects may have an easier route through neglected plumbing.
This is where the popular paper-and-glass trick starts to fall apart. A sheet of paper resting over a drain isn't airtight, and an ordinary drinking glass usually doesn't create a dependable seal against the sink. Even if you manage to cover the opening reasonably well, you're still not solving the underlying issue if the water inside the trap has evaporated. You're covering the top while ignoring the part of the plumbing that was designed to provide the real barrier.
Fortunately, preparing your drains before a vacation doesn't require anything complicated. Before leaving, simply run water through sinks, showers, bathtubs, and other drains that haven't been used recently. Flush toilets, including those in guest bathrooms that might normally sit untouched. If your home has basement or utility floor drains, those deserve attention too. The goal is simple: make sure the traps contain water before the house is left empty.
For a particularly long absence, there are additional ways to slow evaporation in drains that are rarely used. Some plumbing professionals recommend using an appropriate amount of mineral oil in certain infrequently used traps because it evaporates much more slowly than water. A proper drain stopper or well-fitting drain cover may also help reduce airflow across the drain. If you're unsure what is suitable for your particular plumbing system, especially with floor drains or unusual fixtures, getting advice from a plumber is safer than relying on a viral household hack.
It's also worth remembering that drains are only one part of preparing a house before going away. Take out rubbish that could begin to smell, check faucets and visible plumbing for leaks, secure windows and doors, and deal appropriately with appliances that don't need to remain running. Depending on your home, climate, and season, you may also need to consider heating, cooling, water supply, or having someone periodically check the property during a long absence.
That doesn't mean the upside-down glass trick is completely pointless. Covering an unused drain can help keep dust or debris from falling into it, and a proper cover can provide an additional physical barrier. The mistake is assuming that a loose piece of paper and an ordinary glass can replace the protection provided by a functioning, water-filled plumbing trap.
Sometimes the household advice that works best isn't particularly exciting. It doesn't require a strange object from the kitchen or a trick that looks impressive in a fifteen-second video. It's simply understanding how your home was designed to work and taking a few minutes to maintain it properly.
So before your next vacation, don't worry too much about balancing glasses over pieces of paper. Give the forgotten sinks and showers some attention, make sure rarely used traps haven't dried out, and use proper drain covers when they're actually needed.
Your plumbing doesn't need a viral trick.
Most of the time, it just needs a little water.