Drain smells whilst the water drains away normally
Does a drain smell and cleaning doesn't help? Call 070 783 0224 or send a photo of the cupboard under the kitchen sink.
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A drain that smells but isn't blocked almost always has to do with the trap: the bend with water that stops sewer gases. If that water disappears, or there's a layer of dirt in it, you'll smell the sewer. On this page we look at each drain to see what the cause usually is, what you can do yourself and when a new trap or air admittance valve is the solution.
Short answer
If a drain smells whilst water drains normally, the trap has usually dried out or been siphoned empty, or there's a layer of dirt in the trap or drain. First run water into the drain and clean the trap. If the smell returns, especially when another drain or the washing machine runs, water is being siphoned from the trap and an air admittance valve or modified drain will help.
- Rarely used drain? Pour water in: the trap has dried out.
- Air after flushing or when the washing machine pumps? Siphoned trap: ventilation needed.
- Sewer smell everywhere and no source? Then a smoke test helps.
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Which drain smells?
Kitchen sink. Grease and food residue stick to the inside of the trap and the pipe and start to rot. The smell is then more putrid than sewage. Unscrewing and cleaning the trap often helps immediately. If the smell keeps returning, the kitchen drain sometimes needs replacing, with a trap with ventilation and proper connections for the dishwasher and tap.
Shower drain. Hair and soap residue form a layer in the drain and the bend underneath. With a shower that's rarely used, the water in the drain also evaporates. Open the drain, clean it and pour water in.
Washbasin. Often the overflow (the hole at the top of the basin) and the trap. Soap and dirt accumulate in the overflow and start to smell. Flushing with hot water and cleaning the trap helps.
Washing machine drain. The hose sometimes hangs loose in the standpipe without a proper water seal. Sewer odour then enters directly. Lint and detergent residue in the trap also smell after a while. Also read unblock washing machine drain.
Drain in the utility room, cellar or garage. Almost always a dried-out trap, because water rarely goes in. Regularly pour a bucket of water in, or fit a drain with a dry odour seal.
Why a trap isn't doing its job
- Dried out: in a drain that isn't used for weeks, the water evaporates. Classic after a holiday, in a guest bathroom or a cellar drain.
- Siphoned: when a toilet or washing machine discharges a large amount of water at once, it can siphon the traps of other drains. This happens when the pipe doesn't get enough air, for example due to a missing or blocked vent.
- Pushed out: in strong wind or heavy rain, pressure in the sewer can push water out of a trap. You'll smell it especially in bad weather.
- Dirt in the trap or pipe: a layer of grease, soap or hair that starts to rot, without the drain being blocked yet.
- Leak or open connection: a loose trap, a broken rubber seal or a drain without a trap, for example after renovation work.
An air admittance valve (also called a ventilation valve) is a small valve on the drain that lets air in when a lot of water drains away. This prevents the water being sucked out of the trap. It doesn't let sewer gases out. When a trap has been emptied by suction, an air admittance valve is often the solution.
What you can try yourself first
- Run water. Run water for a minute in every drain you rarely use, including in the guest room and the cellar.
- Clean the trap. Put a bucket underneath, unscrew the trap, clean it and screw it back on properly with the rubber ring.
- Clean the drain and overflow. Remove hair and soap from the shower drain and flush the basin overflow with hot water.
- Notice when it smells. Do you smell it especially when the toilet is flushed or the washing machine pumps? Or in strong wind? That tells you a lot about the cause.
- Don't keep pouring. Bleach or drain cleaner only masks the smell briefly at best and can damage rubbers and older pipes.
What does it cost if we fix it?
| Item | Excl. VAT | Incl. 21% VAT |
|---|---|---|
| Call-out charge (first 30 minutes + diagnosis) | € 100 – € 165 | € 121 – € 199,65 |
| Replace kitchen drain (trap with ventilation + connections) | € 516,53 | € 625 |
| Install drain | € 75 | € 90,75 |
| Smoke test drainage system, including report (if the source cannot be found) | € 185,95 – € 268,60 | € 225 – € 325,01 |
| Camera inspection sewer drain | € 225 | € 272,25 |
Guide prices from the PandFix price list (October 2026). Call-out charge is additional: €35 excl. VAT (€42.35 incl.), emergency €65 excl. VAT (€78.65 incl.). Evening or weekend: surcharge €80 excl. VAT (€96.80 incl.). Materials and extra hours only by agreement. You will always hear the price before we start.
If you smell sewer odour everywhere in the house and can't identify a specific drain, read the article sewer smell in house or view smoke test.
Questions about a smelly drain
Why does my drain smell when it's not blocked?
Usually the trap has dried out, been siphoned empty or is dirty. The trap blocks sewer smell with a layer of water. Without that water, or with rotting dirt in it, you smell the sewer.
My kitchen sink only smells after flushing the toilet. How is that possible?
Then the water is sucked out of the kitchen sink trap when the toilet flushes a lot of water. The drain doesn't get enough air. An aerator on the kitchen drain often solves that.
Does soda or vinegar help against a smelly drain?
Hot water with some soda can loosen grease in the trap. But it doesn't solve a dried-out or siphoned trap. Cleaning the trap and ensuring water stays in it works better.
What is an air admittance valve and do I need one?
An air admittance valve is a valve on the drain that lets air in when a lot of water drains away, so the trap doesn't get siphoned empty. You need one if the smell comes after flushing or when the washing machine pumps.
What does a new kitchen drain with aeration cost?
According to our tariff list €516.53 excl. VAT (€625 incl.), including trap with aeration and connections. Call-out charges are additional.
It smells in strong wind. What does that mean?
In windy conditions, the pressure in the sewer can change and push or suck water out of the traps. Often the vent on the roof isn't working properly. A smoke test can show where the air is coming in.
