Across the UK, Europe and the US, millions of people return from sunny holidays to a sour, sewage-like smell wafting from the sink. The culprit is rarely a major plumbing disaster. In most cases, it’s a small, predictable process that starts quietly the moment you lock the door. And a glass, a bit of paper and two minutes of your time can stop it.
Why your sink suddenly smells after a holiday
Plumbers will usually point to one part of your plumbing first: the trap, often called the U-bend or P-trap. That curved section of pipe under your sink, shower or basin is more than an awkward obstacle when you’re trying to unblock it.
Its job is to hold a small pocket of water at all times. That water acts as a plug, blocking foul-smelling gases from the sewer or building pipework from drifting back into your kitchen or bathroom.
When the water in the trap disappears, the barrier between your home and sewer odours disappears with it.
In summer, two things speed up that disappearance:
- Higher temperatures in kitchens and bathrooms, especially in top-floor flats or poorly ventilated homes
- Long periods without using taps, as happens during holidays or work trips
Warm, dry air encourages the water in the trap to evaporate. If you’re gone for a week or two, that thin film of water can reduce so much that it no longer seals the pipe. Once that happens, the path is open for gases to rise straight into the room.
People often blame “blocked pipes” or “rotten food”. Sometimes that’s true, but if the smell fades soon after you’ve run the tap again, evaporation is the more likely cause. Think of your trap like a houseplant: ignore it completely for a couple of weeks in a heatwave and you shouldn’t be surprised it’s bone dry.
The simple glass and paper trick that keeps odours away
There is, though, a very low-tech way to slow this evaporation while you’re on the beach or stuck in airport queues. It uses nothing more than kitchen roll and a drinking glass.
How to set it up before you leave
Do this on the day you travel, ideally just before you walk out of the door:
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This makes a loose, almost hermetic “cap” over the plug hole. The damp paper helps create a seal, while the upside-down glass traps a small pocket of air over the drain.
The glass-and-paper cap slows the contact between warm room air and the water in the trap, cutting evaporation dramatically.
The water in your pipes will still evaporate, but far more slowly. For most holiday lengths — anything from a long weekend to a two‑week break — that’s enough to keep the trap doing its job.
Plumbers tend to like this trick for three reasons: it costs nothing, it takes seconds, and it doesn’t interfere with the actual pipework. Remove the glass and paper when you get back, run the tap, and everything goes back to normal.
What about toilets and showers?
Toilets rely on exactly the same principle as your sink: a standing pool of water acting as a barrier. To protect them before a trip:
- Flush once to refresh the bowl.
- Close both the seat and lid firmly, which reduces warm air circulation over the water surface.
For showers and bath drains, you can use a similar approach to the sink:
- Pour a bit of water down the drain just before leaving.
- Cover the waste with a flat object – a rubber mat, a plastic lid or even cling film – taped at the edges if needed.
Extra habits that keep your sink healthy all summer
Beyond the glass and paper, a few small routines can make a big difference to smell and long-term pipe health.
A thin layer of oil as a protective film
Some professional cleaners suggest adding a spoonful of vegetable oil to each drain before travelling. Because oil is lighter than water, it floats on top and forms a thin layer that slows evaporation even further.
One tablespoon of cooking oil over the trap water acts like a lid, reducing how fast it can disappear.
Use a basic oil you already have at home: sunflower, rapeseed or olive oil all work. Avoid pouring in large quantities, as you don’t want to contribute to fat build-up deeper in the system.
A quick pre-holiday clean for the pipes
Rotting food scraps stuck just inside the drain can still produce a nasty smell, even if the trap works perfectly. A short cleaning routine the day before you leave can prevent that.
| Step | What to do | Why it helps |
|---|---|---|
| 1 | Pour 2–3 tablespoons of bicarbonate of soda into the plug hole | Loosens light grease and absorbed odours |
| 2 | Add a small glass of white vinegar | The fizz helps shift residue on the pipe walls |
| 3 | Leave for 15–20 minutes | Gives time for the reaction to act on deposits |
| 4 | Rinse with very hot (but not boiling) water | Flushes dissolved grime away |
This is not a cure for serious blockages, but it reduces the organic matter that can ferment while you’re gone, particularly in kitchen sinks where fats and food particles are common.
When a bad smell points to a bigger issue
Sometimes the odour that greets you after a trip is more than just evaporated water. If smells persist long after you’ve run the taps and flushed the toilet several times, something else may be wrong.
Warning signs worth taking seriously include:
- Gurgling sounds from the pipes when you drain water
- Slow drainage in several fixtures at once
- Smell of gas or chemicals rather than just “drain odour”
- Visible leaks or damp patches under sinks
Those can signal deeper blockages, poorly vented pipes or damaged seals. In that case, a glass and a bit of paper won’t fix the root cause. A licensed plumber can check whether traps are correctly installed and whether the ventilation stack — the pipe that lets air in and out of the system — is working.
Turning a tiny habit into a travel routine
Think of the glass-and-paper trick as belonging to the same checklist as locking the windows and emptying the fridge. It’s quick, it prevents an avoidable annoyance, and once you’ve done it once, it becomes automatic.
Picture two scenarios. In the first, you come back from a long drive, open the door and get hit by that familiar, stale, drain-like whiff. You start running taps, lighting scented candles and wondering if something has burst. In the second, you drop your bags, the air smells neutral, and the only surprise is the pile of post on the mat. The small act in front of your sink, 30 seconds before leaving, is what separates the two scenes.
If you already struggle with strong smells, live in a hot top-floor flat, or keep pets that stay home while you’re away, this tiny trick can make their environment more comfortable as well. Combine it with simple pipe care and you cut both odours and the chances of future plumbing bills.