Sewage smell in the kitchen

31 Mar 2015
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United Kingdom
I've been haunted by an intermittent sewage smell in the kitchen ever since I moved in.

My first suspect was the waste pipe that goes from the kitchen sink into the outside drain. The drain was blocked so I thought it was the smell from the drain that was coming up the drain pipe and into the kitchen. I had the drain unblocked and it didn't quite solve the problem. The drain, even though unblocked, still smells bad at times.

I put on a cap on the washing machine waste outlet pipe, which was 'open' (no washing machine there yet); not really a proper cap, just a plastic yogurt cup upside down. That didn't help either.

I noticed the smell wasn't coming from any specific place (such as the sink or washing machine waste pipe) but concentrated in different parts of the kitchen. One time it would stay near the back door, another time it would hover above the worktop, etc.

Another suspect was the air brick, which is located next to the drain. I thought maybe the smell goes under the kitchen floor via the air brick when the wind direction is right, and enters the kitchen through the gaps in the concrete floor. So I put up a makeshift barrier made of a brick and old clothes to stop the air from the drain getting into the air brick. For a while I thought it had helped, but the smell is back again.

Any ideas of what it might be, please?
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photos pleased, of drains inside and out.

Have you got an extension that might be built over drains? Have you got a "manhole?"

Have you looked and sniffed under the floor?
Photo of drains outside from a couple of months ago before the drain was unblocked:


The white pipe is kitchen waste, the downpipe on the left is bathroom waste, the one of the right is for rainwater.

No extension... yet. Thinking of getting one (most likely a conservatory), looks like I'll have to have the drains checked properly before I do?

I haven't got a manhole.

The floor is concrete (only in the kitchen, it's wooden throughout the rest of the ground floor). I haven't looked under it.

I think the smell gets worse just after using the kitchen tap - I open it, let the water run for a few seconds, close it and the smell appears or intensifies. But it's really hard to tell as it's so unpredictable, there are probably several variables here.

I must add I'm planning on having a complete refit of the kitchen within the next few weeks, so that would be a good opportunity to investigate the smell issue if you guys can suggest possible culprits. The works will be done by a company, not myself.
have you cleaned the plughole and overflow of the sink, by packing with Washing Soda Crystals, moistening with boiling water, and leaving overnight?

Have you taken the sink trap or U-bend off and cleaned it?

Is the floor under the sink damp?

Does anybody ever tip cooking fat or oil down the sink?

Is the soil near the gully damp, or sunken, or patched up?
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Thanks John.

I haven't cleaned the sink with Washing Soda Crystals, might well do that but that doesn't seem to be the problem here as it's a sewage smell, the same smell that comes from the drain?

I've cleaned the sink trap recently (like a week ago) and a plumber did the same in April while changing the tap.

I don't tip fat or oil down the sink, but the previous occupier may have (before February this year)?

The area around the drain is paved with patio blocks and doesn't appear to be sunken. If it was damp I probably wouldn't know.
If that's the case here, would that mean the smell is coming from the soil underneath the house because it's flooded with foul water leaking from the gully, or is it that the leak is the reason why the drain itself smells, and the smell is getting into the house via the waste pipes?
unlikely to be through the waste pipes, because they should all have traps under the plughole.
A photo of waste under kitchen units would help, if the washing machine waste U bend is clogged the machine may pump out all the water from the u bend [siphoning]allowing smells back thru it.
There is no washing machine connected. The washing machine waste pipe has an open end directed upwards, so smells can indeed get inside through it. I put an upside-down yogurt cup on it to stop them, but I'm not sure how effective that is.

Isn't the drain not supposed to smell in the first place?
Here is a photo.

The horizontal-ish white pipe is the sink waste and the one coming out of it with the plastic cup is the washing machine waste.


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Here is a photo.

The horizontal-ish white pipe is the sink waste and the one coming out of it with the plastic cup is the washing machine waste.
Problem is now obvious, there is no trap on the washing machine waste which will allow fumes from drain straight up the pipe, also the T is fitted back to front meaning the waste water will be pumped in the wrong direction away from the drain.The cup won't stop the smell.

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