Before locking the door and heading for the beach, one tiny detail in your kitchen can spare you a very smelly return.
Many holidaymakers come home to clean sheets and a tidy flat, yet are greeted by a stubborn whiff of sewer gas from the sink. The cause is rarely dramatic plumbing failure. In most cases, it comes down to heat, evaporation and a small bend in the pipe you hardly ever think about. A simple trick with a glass and a sheet of paper can make a huge difference during a long summer break.
Why your sink smells so bad after a holiday
The main suspect, according to plumbers, is almost always the trap under your sink – that U-shaped bend in the pipe, known as a “P-trap” or “siphon”.
Its job is surprisingly simple. The bend holds a permanent pool of water. That water acts as a liquid plug, blocking foul-smelling gases from the sewer side of the system.
The trap under your sink is a protective water barrier. When that barrier evaporates, the smells rush straight into your kitchen.
During a hot summer, especially in a closed, poorly ventilated flat or house, that protective water starts to evaporate. If no one runs the tap for days or weeks, the level in the trap drops. Once it gets too low, the gas barrier breaks.
That’s when the characteristic “drain” smell creeps out of the plughole and into the whole room. In multi-storey buildings, this can be worse: pressure changes in the shared pipework can literally pull water out of traps on higher floors.
The same thing happens to other water seals in your home: shower drains, bath drains, floor drains, even unused toilets. Any place where standing water blocks the pipe can dry out if left alone in a warm property for long enough.
The glass and paper trick that slows evaporation
To keep that protective water in place for as long as possible, you need to reduce its contact with warm, dry air. That is where the glass-and-paper hack comes in.
How to set it up before you leave
- Run the tap for a few seconds so the trap under the sink is completely filled.
- Take a sheet of kitchen paper or another absorbent paper.
- Dampen the paper slightly under the tap; it should be moist, not dripping.
- Lay the paper flat over the sink drain, covering the plughole.
- Place a glass upside down on top of the paper so it sits firmly over the drain.
The moist paper helps form a soft seal on the metal or ceramic around the plughole. The inverted glass then acts like a mini bell jar, reducing direct airflow over the drain opening.
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This improvised cover creates a kind of lid over the plughole, so the water beneath it evaporates far more slowly.
Plumbers like this approach because it is cheap, reversible and doesn’t block the pipe itself. You are not stuffing anything into the drain; you are just limiting air exchange at the very top.
For toilets, the principle is similar. You already have a water seal in the U-shaped section of the pan. Before leaving, flush once, then close both the seat and the lid. That simple act slows evaporation from the bowl and makes it harder for odours to escape if the level drops slightly.
Extra steps to keep drains fresh while you are away
The glass and paper trick tackles the evaporation problem, but a bit of basic maintenance before you go can reduce smells from residue as well.
Using oil as a protective layer
Some plumbers recommend pouring a small amount of vegetable oil down each drain just before leaving.
- Use roughly one tablespoon of oil per drain.
- Olive, rapeseed or sunflower oil all work.
- Pour it gently so it settles on top of the water in the trap.
Because oil is lighter than water, it floats on the surface and forms a thin film. That thin film acts as a second barrier, slowing evaporation even more and isolating the water below from air and heat.
A tablespoon of oil over the trap water works like a lid, reinforcing the protection that your glass and paper already provide.
A quick clean to remove future odours
Smells do not only come from sewer gas. Food scraps, grease and soap scum can rot inside the pipes, creating their own bouquet of odours. A fast cleaning routine before heading off can help:
| Step | Action | Purpose |
|---|---|---|
| 1 | Sprinkle 2–3 tablespoons of bicarbonate of soda into the drain. | Loosens light deposits and neutralises some smells. |
| 2 | Pour a small glass of white vinegar on top. | Fizzing reaction helps dislodge residue in the upper pipe. |
| 3 | Leave for 15–20 minutes. | Gives the mixture time to work. |
| 4 | Rinse with a kettle of hot (not boiling) water. | Washes loosened debris away and clears the trap. |
This method avoids harsh chemical unblockers, which are stronger but can be aggressive to older pipework and not ideal for septic systems.
What happens if you skip these steps
Ignoring the traps for a two-week trip rarely leads to dangerous situations, but the consequences are far from pleasant. You may walk into a kitchen that smells like a damp cellar, just as the heat outside is pushing you towards open windows and fresh air.
In extreme cases, a dried-out trap can allow not only smells but also tiny insects to crawl up from shared pipes, particularly in older buildings with questionable maintenance. For those with allergies or respiratory issues, strong odours and mouldy air can be more than just a nuisance.
On top of that, if grease and food residues are left sitting for long periods, they can harden. That can turn a simple smell problem into a genuine blockage, potentially requiring professional intervention once you are back.
When you travel often or rent out your place
People who travel frequently, or who rent their flat on short-term platforms, face these issues more often. Constant empty periods mean traps have more chances to dry out between guests.
In those situations, it can make sense to place a short checklist by the front door for your own use, or for guests who are leaving:
- Run taps for 30 seconds in sinks and showers.
- Check that plugholes are covered with glass and paper if the place will stay empty.
- Close all toilet lids.
- Take out kitchen rubbish and clean the filter in the dishwasher.
These habits reduce the risk of nasty surprises for you or the next person walking through the door, and they protect the plumbing from repeated drying and re-wetting cycles.
Understanding a few useful terms
Two technical expressions often appear in discussions about smells from drains. The first is “trap seal”, which simply means the depth of water sitting in the bend of the pipe. The deeper it is, the longer it takes to evaporate and the better it blocks gases.
The second is “siphoning”. This happens when the flow of water in one part of the system pulls water out of a trap somewhere else. In blocks of flats, a powerful flush in a neighbour’s toilet can sometimes reduce the seal in your own trap, especially if the pipes are old or poorly designed. That is another reason why extra protection, like the glass and paper trick, can help during long absences.
Small routines that add up
Taken alone, one inverted glass or a spoonful of oil looks trivial. Put together with a quick pre-holiday clean and a check on toilet lids, these actions build a solid defence against odours and minor plumbing issues.
The benefit shows up precisely when you need it most: late at night, suitcase in hand, when all you want is a shower and a drink of cold water, not an unexpected hit of drain smell greeting you in the kitchen.
Originally posted 2026-02-23 19:13:28.