Domakihub Eliminate Bad Smells from Kitchen and Bathroom Drains
Fix drain odour at the root with a simple DIY flush — and know when to call a plumber.
Reviewed by Domakihub cleaning pros · 2026-06-23 · 5 min read
A sour or sulphurous smell rising from a drain is one of the most common complaints in Greek homes, holiday apartments, and hotel rooms — and it rarely means the pipe is blocked. The video above walks through what a plumber sees when these smells appear; this guide gives you the step-by-step flush you can do yourself today, plus a clear explanation of the two situations that need a professional. Whether you manage a single bathroom or a portfolio of holiday rentals, addressing the root cause keeps guests comfortable and prevents small problems from becoming expensive ones.
Why Drains Smell: Biofilm and Sewer Gas
The most common culprit is biofilm — a slick layer of soap residue, grease, hair, and bacteria that coats the inside of the drainpipe just below the drain cover. As bacteria break down organic matter, they release hydrogen sulphide, the gas responsible for the rotten-egg smell you notice after the tap runs. In Greek holiday properties that sit empty between rentals, biofilm builds up quickly because there is no regular water flow to flush it away.
The second cause is sewer gas entering the room through a dry P-trap. The P-trap is the curved section of pipe beneath every sink, shower, and toilet — it holds a small plug of water that physically blocks sewer gas from rising into the room. When a drain is unused for more than two to three weeks, that water plug evaporates and the barrier disappears. This is extremely common in seasonal rentals on the islands, where a property may be empty for months over winter.
When the Problem Is a Blocked Vent Stack
Every plumbing system needs a vent stack — a vertical pipe that exits through the roof and equalises air pressure so water drains freely without sucking the P-traps dry. If that vent becomes blocked by debris, bird nests, or a cracked pipe, negative pressure builds up in the system and pulls water out of every P-trap in the building at once. You will notice multiple drains in different rooms smelling at the same time, or a gurgling sound when a toilet flushes.
A blocked or damaged vent stack is not a DIY repair. It requires access to the roof, specialist inspection, and in some cases a camera survey of the pipe. If the baking-soda flush described below does not solve the smell, or if several drains are affected simultaneously, contact a licensed plumber before the situation worsens.
DIY Baking-Soda and Vinegar Drain Flush: 5 Steps
- 1
Clear and rinse the drain opening
Remove the drain cover and pull out any visible hair or debris with gloved hands or a small hook tool. Run hot tap water for 30 seconds to wet the pipe walls and loosen surface grease. This primes the drain so the cleaning agents can reach the biofilm rather than sitting on top of solid blockages.
- 2
Pour boiling water down first
Carefully pour one full kettle of boiling water directly into the drain in a slow, steady stream. The heat melts grease buildup that soap and cold water leave behind. For plastic PVC pipes, use the hottest water your tap produces rather than a full boil, since repeated boiling-water flushes can soften PVC joints over time.
- 3
Add baking soda, then white vinegar
Measure half a cup (about 120 ml) of bicarbonate of soda and pour it down the drain, pushing it in with a spoon so it coats the pipe walls. Immediately follow with half a cup of white vinegar. The two react to produce carbon dioxide foam that scrubs the biofilm off pipe walls and neutralises the bacteria producing the odour. Place a cloth or drain plug over the opening to force the foam downward rather than back up.
- 4
Wait 20 minutes, then flush with hot water
Leave the mixture to work for at least 20 minutes — longer if the smell is strong. Then pour another kettle of hot water to flush the loosened biofilm and neutralised residue fully through the trap and into the main drain. Repeat the baking-soda-and-vinegar cycle a second time for drains that have been neglected for several months, as a single treatment may not remove all the buildup.
- 5
Refill dry P-traps and add a monthly maintenance flush
If a drain has been unused, simply running the tap for 60 seconds refills the P-trap water plug and seals out sewer gas immediately. For holiday properties, brief all housekeepers to run every tap and flush every toilet before a new guest arrives. Scheduling the baking-soda flush once a month takes under five minutes and prevents biofilm from returning — far cheaper than a call-out fee.
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FAQ
- Can I use commercial drain unblocker instead of baking soda and vinegar?
- Chemical drain unblockers (caustic soda or sulphuric-acid based) are designed to dissolve solid blockages, not biofilm. They are aggressive, harmful to older pipes, and dangerous if splashed. For odour caused by biofilm, the baking-soda-and-vinegar method is more effective, safer, and far cheaper. Reserve chemical products for an actual blockage, and follow the label instructions carefully.
- How do I know if my P-trap is dry rather than a biofilm problem?
- A dry P-trap produces a strong, constant sewer smell even when the drain is not in use, and the smell disappears almost instantly once you run the tap for a minute. Biofilm odour, by contrast, tends to be strongest immediately after water runs through the drain and fades when the drain is dry. If running the tap for 60 seconds eliminates the smell entirely, a dry trap was the cause.
- How often should I do the baking-soda flush in a Greek holiday rental?
- Once a month during the rental season keeps drains odour-free with minimal effort. Before opening the property after a long winter closure, do two flushes on consecutive days to clear any accumulated buildup, and run all taps for at least two minutes each to refill every P-trap. Add this to the opening-week checklist alongside checking water heaters and testing smoke detectors.