Coming home from a relaxing trip should feel great, but sometimes you open the front door and get hit with an awful smell that makes you wish you were still at the beach. Your trash is empty, nothing spoiled in the fridge, and you cleaned before you left. So where’s that stench coming from? The answer might surprise you: it’s probably your sink drain. When water sits unused in your plumbing for too long, the natural barrier that keeps sewer gases out of your home can dry up, letting those nasty smells creep into your kitchen or bathroom.
Your P-trap is drying out without you knowing it
Every sink in your home has a curved section of pipe underneath called a P-trap, and it does something pretty smart. This U-shaped bend holds a small amount of water that acts like a plug, stopping smelly sewer gases from backing up through your drain and into your living space. When you use your sink regularly, fresh water constantly refills this trap, keeping that barrier in place. It works automatically without you thinking about it, which is why most people never realize how important this little bit of standing water actually is.
The problem starts when you leave for vacation and stop using your sinks. Without fresh water running through, the water in the P-trap starts evaporating. In normal conditions, this takes about a month, but dry climates or winter heating can speed things up. Once that water disappears, there’s nothing stopping the gases from your sewer line or septic system from floating right up into your house. Guest bathrooms, basement floor drains, and other rarely used fixtures are especially prone to this issue since they might already be partly dried out before you even leave.
The paper towel and glass trick keeps moisture where you need it
Before you head out on your next trip, take two minutes to do this simple trick at every sink: fill a glass with cold water and pour it down the drain to make sure the trap is full. Then, wet a paper towel and lay it flat over the drain opening. Finally, place the empty glass upside down on top of the paper towel. That’s it. This setup works because each part solves a specific problem. The water you poured down ensures the trap starts full, the damp paper towel absorbs moisture as it evaporates and keeps it near the drain opening instead of letting it escape into the air.
The glass creates a seal that holds everything in place and slows down evaporation even more. Some people fill the glass with water before flipping it upside down, which adds extra moisture to the barrier. Others use extra-absorbent paper towels without additional water. Both methods work well, so you can experiment to see which one is easier for your setup. The key is creating multiple layers of protection against evaporation, giving your P-trap the best chance of staying full while you’re enjoying your time away from home.
Winter months and dry climates make this trick even more important
You might think evaporation happens faster in summer, but winter is actually when dry P-traps become most common. When you run your heating system, it pulls moisture out of the air inside your home, which speeds up evaporation in your plumbing. If you live in Arizona, Nevada, or other dry states, this problem gets even worse because the air already has low humidity year-round. A trap that might normally last a month could dry out in half that time under these conditions, meaning even a two-week vacation could leave you with smelly drains.
Older homes with S-traps instead of P-traps face this issue more often too. S-traps look similar but the physics of their shape makes them more likely to lose their water seal. If you’re not sure what type of trap you have, look under your sink. A P-trap curves down and then back up before heading into the wall, while an S-trap curves down and continues straight down through the floor. Either way, the paper towel and glass method helps, but S-trap owners might want to take extra precautions like adding mineral oil to the drain before leaving.
This method also keeps bugs from crawling up your drains
Here’s something nobody wants to think about: when your P-trap dries out, it doesn’t just let smells through. Bugs can crawl up from your sewer line or septic system too. Flies, cockroaches, and other insects sometimes make their way through dried-out drains and into your home while you’re gone. Coming back to find bugs in your sink or scattered around your kitchen is almost as bad as the smell. The paper towel and glass barrier blocks these unwanted visitors just as effectively as it blocks odors.
When bugs try to come up through a covered drain, they either die in the pipe or get trapped under the glass. You might find a few dead insects in your sink when you return, which isn’t pleasant, but it beats having them roaming freely through your house for days or weeks. This added pest control benefit makes the trick worthwhile even if you’re only leaving for a long weekend. It takes less time than loading your luggage into the car, and it can save you from some truly unpleasant surprises when you get home.
Don’t forget about floor drains and laundry rooms
Most people remember their kitchen and bathroom sinks when prepping for a trip, but floor drains in basements, laundry rooms, and garages get overlooked all the time. These drains have P-traps too, and since they’re used even less frequently than guest bathroom sinks, they’re often already halfway dry before you leave. A floor drain that hasn’t seen water in months could start smelling within days of your departure. Check every drain in your house, not just the obvious ones, and give them all the same treatment.
For floor drains, you might need to adjust the technique slightly since you can’t balance a glass over a drain cover. Pour the water down as usual, then place a damp towel or cloth over the drain and weigh it down with something flat and heavy, like a brick or a heavy book wrapped in plastic. The goal is the same: slow down evaporation and keep that water seal intact. Utility sinks in garages or workshops need attention too. Any drain that connects to your main plumbing system can be a source of sewer gas if the trap runs dry.
Adding mineral oil creates an extra layer of protection
If you’re planning a longer trip or live somewhere especially dry, consider adding one more step before placing your paper towel and glass. After pouring water down the drain, add about a teaspoon of food-grade mineral oil. The oil floats on top of the water in your P-trap and creates a barrier that dramatically slows evaporation. Water can’t evaporate through oil, so this protective layer can keep your trap full for much longer than water alone would last.
You can find food-grade mineral oil at most grocery stores or pharmacies, usually in the section with digestive health products. Make sure you get food-grade, not the stuff meant for cutting boards or other household uses. A small bottle costs less than ten dollars and will last for years since you only need a tiny amount per drain. When combined with the paper towel and glass method, this creates a nearly foolproof system that can protect your home even if you’re gone for a month or longer.
Cleaning your drains before you leave helps prevent stubborn smells
Sometimes drain odors happen even when your P-trap has plenty of water, especially if there’s buildup stuck to the inside of your pipes. Before a long trip, take a few minutes to give your drains a quick cleaning. Pour one cup of baking soda down each drain and let it sit for about 15 minutes. Then add half a cup of vinegar, which will fizz and bubble as it reacts with the baking soda. This combination breaks down grease, soap scum, and other residue that can start to smell when it dries out.
After letting the vinegar work for another 15 minutes, flush everything with hot water for at least a minute. This process removes the bacteria and gunk that causes odors, giving you a fresh start before you leave. If you have a garbage disposal, use a long brush with warm soapy water to scrub around the opening, then run a mixture of water and vinegar through it before flushing with cold water. Starting with clean drains means even if some water does evaporate while you’re gone, there’s less dried-on material to create bad smells.
What to do when you get home from your trip
When you return from vacation, remove the glass and paper towel from each drain and run cold water for at least a minute. This flushes out the pipes, refills the P-trap completely, and washes away any residue that might have dried on the sides of the drain while you were gone. Running the water also helps you check that everything is working properly and that no other plumbing issues developed while you were away. It’s a simple step that takes barely any time but ensures your drains are back to normal functioning.
If you followed all the steps before leaving but still notice a smell when you get home, the problem might not be your P-trap. Check your garbage disposal, dishwasher drain, and washing machine hoses, which can all develop odors if food or debris is stuck inside. Sometimes smells that seem to come from drains are actually coming from nearby appliances or the overflow opening near the rim of your sink. A thorough cleaning of all these areas should take care of any lingering odors and get your home smelling fresh again.
How often should you use this trick
You don’t need to do this every time you leave the house for a day or even a weekend. For trips shorter than four or five days, your P-traps should stay full on their own unless you live in an extremely dry climate or are dealing with a drain that rarely gets used. The paper towel and glass method is really meant for vacations lasting a week or more, or any time you’ll be away long enough that evaporation could become an issue. That said, it only takes a few minutes, so there’s no harm in doing it for shorter trips if you want extra peace of mind.
For drains you hardly ever use, like that sink in the guest bathroom that only sees action when relatives visit, consider running water down them once a month even when you’re home. This keeps the trap full and prevents the kind of buildup that leads to smells. If you have a vacation home that sits empty for months at a time, definitely use the paper towel and glass trick before you leave, along with the mineral oil addition. Taking these small steps protects your investment and ensures you always come back to a home that smells clean and welcoming.
Nobody wants their vacation afterglow ruined by walking into a house that smells like a sewer. Spending two minutes before you leave to fill your drains, place damp paper towels over them, and set glasses on top is one of the easiest ways to prevent this problem. Your P-traps will stay full, sewer gases will stay where they belong, and bugs won’t have an open invitation into your home. When you return, just run some water and enjoy being back in a fresh-smelling house.
