Looking through the reviews on TripAdvisor you would be tempted to think that the boutique hotels in Paris suffered from some kind of horrible sewage problem.

good location, bad smell


How does a review like that happen? Suppose an American couple checks into a boutique hotel in gay Paris. Everything is fine the first day. Then the second day they start to notice an unwelcome sewer-y odor in bathroom. At first they assume it was their own issue (as it were), but the smell doesn’t go away and they figure bad plumbing. And later write a bad TripAdvisor review.

There’s a disconnect here: how can a hotel cost $350 a night for a tiny room and then smell like an open sewer on a hot day? It’s because Americans don’t understand bidets (we don't have them). So we don’t usually use them. And that is the root of the problem.

Hold on, let me explain.

All bathroom fixtures (shower, toilet, sink, bidet) carry wastewater to the sewer via pipes. Sewers are stinky places, and the sewer gasses can come up through the pipes, and into surrounding spaces. Plumbers figured out how to fix this hundreds of years ago with something called the P-trap.

A P trap is a U-turn in a pipe—you’ve probably seen them under your kitchen sink.

Image from http://www.planta1.com/blog/how-to-deal-with-the-p-trap-in-revit-mep/

The P-trap—Elegant Solution to an Ancient Problem

The P-trap retains just enough water from the last use of the fixture to maintain a watertight seal in the U shape. The gas coming up from the sewer is prevented from entering the room by the water in the P-trap. If the fixture isn’t used for a while, the water in the P-trap will evaporate. If enough water evaporates from the P-trap it won't form the seal necessary. That seal is what keeps the gas from coming up from the sewer, and out into your boutique hotel room. The evaporating water in the P-trap is the culprit!

So the fix is easy.

Add some water to the bidet once a day to refill the P-trap. The easiest way to do this is to either turn the bidet on for a second, or just use it.

A friend of mine says we should all have bidets. “If you got poo on any other part of your body, would you be satisfied just wiping at it with paper?”

There you have it, another travel tip from your world-travelling Security Evangelist (and DiY travel blogger).

P-Trap diagram used with permission from Planta1 online consulting.