Home/ Blog/ Drain smell in a hotel room — cause, reviews and a permanent fix
Hotels & HoReCa 9 June 2026 · 4 min read

Drain smell in a hotel room — cause, reviews and a permanent fix

The room is spotless, and the guest still writes “it stinks of sewage”

The worst sentence in a review is not “a bit dated” — it is “the room was clean, but it stank terribly of sewage”. It stings because it implies poor hygiene, when the truth is the opposite: housekeeping did their job, but the odour is coming out of the floor drain and has nothing to do with cleanliness. For a hotel that means a lower score and lost bookings.

Where the odour comes from

Every bathroom has a trap — water sitting in a bend of pipe that holds sewer gases down. In rooms that stand empty (between guests, out of season, unsold units) the water in the trap evaporates. The trap runs dry, the barrier disappears, and hydrogen sulphide (the rotten-egg smell), methane and ammonia come up from the main sewer into the room. Carpets, curtains and bed linen absorb them, so the odour is waiting for the guest the moment the door opens.

Air fresheners do not solve the problem — they simply add perfume on top of a sewer smell, which guests recognise and mark down especially harshly.

Why one review hurts for a whole season

Booking and similar platforms rank properties by average score and recency. A single negative review containing the word “sewage” in the first week of the season pulls the average down and pushes you further down the results — fewer views, fewer bookings, for months. Multiply that across several rooms and you have a measurable financial loss that far exceeds the cost of fixing it.

The pre-season protocol that does not hold

The standard answer: before the season the technical team goes through every room and runs water into every drain. For a 200-room hotel that is 2–3 days of work for a crew. The problem: as soon as the water evaporates again (and in unsold rooms that is a matter of weeks), the odour is back. Pre-season preparation turns into a permanent job, and the job is never finished.

The permanent fix: a passive silicone seal

The Green Drain™ silicone seal works mechanically; it does not depend on water sitting in the trap. In the closed position it blocks sewer gases even when the trap is completely dry, and it opens only when water flows down through it. For a hotel, in concrete terms:

The investment pays for itself with the first negative review you avoid. A detailed calculation is set out in the article ROI: passive floor drain protection.

Source and method
Based on research published by Green Drain Inc. and adapted for the Croatian market and the EU regulatory framework by Green Flow d.o.o., exclusive distributor of Green Drain™ for the Adria region. Standards referenced: EU MDR 2017/745, EN 1253, ASSE 1072-2020, HACCP, BRC and IFS. Statistics from the Croatian Bureau of Statistics (DZS) and the Croatian Institute of Public Health (HZJZ) where indicated.

Frequently asked questions.

Why does a hotel room smell of sewage even though it is clean?
The cause is a dried-out trap in the floor drain or the shower. In empty rooms the water in the trap evaporates, the barrier disappears and gases (H2S, methane, ammonia) enter the room, where textiles absorb them — so the guest notices the smell immediately, regardless of how clean the room is.
Why does flushing with water not solve the problem for good?
Water refills the trap, but it evaporates again. In rooms that are not sold every day the odour comes back, so the pre-season protocol becomes a permanent job with no guarantee.
What does a negative review about odour actually cost?
It lowers the average score and pushes the property further down the Booking results, which reduces views and bookings for the whole season. The cost of sorting the drains out is almost always lower than the loss caused by a single negative review.
How do you permanently prevent drain odour in guest rooms?
By fitting a passive silicone seal with a one-way valve (Green Drain) into every floor drain. It blocks gases even when the trap is dry, works without water and needs no maintenance — so there is no manual flushing of rooms.
How long does installation take in a hotel with a lot of rooms?
Around 30 seconds per drain, with no tools. For 200 rooms with three drains each that is about 5 hours of work for one person, done once, with no water consumption (also relevant for LEED/BREEAM).

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