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Kitchen extraction cleaning - odours
A smell coming from the kitchen drains is unpleasant and off-putting - and it usually points to the drainage and grease trap, not the extraction. Drain smells are a separate issue from your ductwork. But a stale grease smell in the kitchen can sometimes be the duct rather than the drains. Here is why drains smell, and how to tell a drain problem from a duct one. This is general guidance.
The short answer
A smell from the kitchen drains is a common and unpleasant problem - and it's worth understanding, both because it usually has a straightforward drainage cause and because it's sometimes confused with (or masks) a smell from the extraction. Here's why drains smell, and how to tell a drain problem from a duct one. This is general guidance; drainage issues are a matter for drainage/plumbing services. Drains smell: usually a drainage issue. First, the honest point: smelly kitchen drains are, in most cases, a drainage problem, not an extraction one. This page is in the extraction series, but drain odour is largely a separate issue from your ductwork - so it's worth being clear where the cause usually lies. Why drains smell. Kitchen drains smell mainly because of what goes down them and builds up: Fats, oils and grease (FOG). Grease poured or washed down the drains builds up in the pipes, gullies, traps and grease trap, where it accumulates and decomposes, giving off unpleasant smells. A blocked or dirty grease trap is a classic source of drain odour. Food waste. Food debris going down the drains rots and smells. A dry trap. The water seal in a trap or gully (which normally blocks sewer gases) can dry out if unused, letting sewer smells up. A blockage or fault. A partial blockage (often grease/food) traps decomposing matter; a drainage fault can also let smells through. So the smell usually comes from grease and food building up (or a dry trap or blockage) in the drainage system. How to fix smelly drains. The fix is drainage maintenance, not extraction cleaning: Clean the drains, gullies and grease trap - removing the grease and food build-up that causes the smell (a regular part of a kitchen deep clean and drainage maintenance - as covered in the floor-drains-and-gullies-in-every-deep-clean page). Manage the grease trap - keeping it emptied and cleaned (a common odour source if neglected - as covered in the grease-trap-management page). Keep traps topped up - running water to maintain the water seals. Clear any blockage - and address drainage faults (a job for drainage/plumbing services). Avoid putting FOG down the drains - reducing the build-up at source (as covered in the how-fats-oils-and-grease-cost-you-at-the-drain page). The connection to the extraction. There is one connection worth noting, though. A stale, greasy smell in the kitchen can sometimes come from the extraction ductwork rather than the drains - grease decomposing in a grease-laden duct can give off a stale smell (as covered in the smell-of-stale-grease and smell-that-tells-you-grease-has-reached-the-duct pages). So a persistent stale grease smell isn't automatically the drains - it could be the extraction. How to tell which. So if you have a persistent smell, work out its source: Where is it strongest? A smell strongest at the drains, gullies or sink points to the drainage; a smell strongest near the canopy or when the extraction runs points to the duct. What's it like? A sewer-like or rotting-food smell suggests drains; a stale, greasy, cooking-fat smell can be either but leans toward grease (drains or duct). When does it occur? A smell when water drains or when unused traps dry out suggests drains; a smell tied to the extraction running suggests the duct. So identify whether it's a drainage smell (address the drains and grease trap) or a duct smell (address the extraction). The takeaway. So smelly kitchen drains are usually a drainage/grease-trap issue - cleaned and managed through drainage maintenance, separate from your extraction. But a stale grease smell in the kitchen can sometimes be the extraction duct rather than the drains, so if the source isn't clearly the drains, consider the ductwork. So identify the real source - drains or duct - and address the right one. This is general guidance.
Key points
Usually a drainage issue
The honest starting point is that smelly kitchen drains are, in most cases, a drainage problem, not an extraction one. Although this page sits in the extraction series, drain odour is largely a separate issue from your ductwork - so it's worth being clear that the cause usually lies in the drainage system (the drains, gullies, traps and grease trap), not the extraction.
This matters because it's easy to lump all kitchen smells together, but a drain smell and a duct smell are different problems with different causes and fixes. A drain smell is a drainage-maintenance matter (cleaning the drains and grease trap); it's not something extraction cleaning addresses. So if your drains smell, the answer lies in the drainage, not the ductwork. That said, there's a connection worth knowing about - a stale grease smell can sometimes be the duct - which is covered later (and is the reason this topic touches the extraction series at all). So usually a drainage issue - not the extraction, in most cases - is the key framing: address a drain smell as the drainage problem it usually is. The following sections cover why drains smell, how to fix it, and how to tell a drain smell from a duct one. So a drain smell is usually a drainage matter, not the extraction. This is general guidance.
Why drains smell
Kitchen drains smell mainly because of what goes down them and builds up. Fats, oils and grease (FOG): grease poured or washed down the drains builds up in the pipes, gullies, traps and grease trap, where it accumulates and decomposes, giving off unpleasant smells. A blocked or dirty grease trap is a classic source of drain odour (as covered in the grease-trap-management page). Food waste: food debris going down the drains rots and smells.
Other causes: a dry trap - the water seal in a trap or gully (which normally blocks sewer gases) can dry out if that drain is unused, letting sewer smells up; a blockage - a partial blockage (often grease and food) traps decomposing matter and smells; and a drainage fault - which can let smells through. So the smell usually comes from grease and food building up in the drainage system, or from a dry trap or blockage. Grease is the biggest culprit in a commercial kitchen (a lot of it goes down the drains, and it builds up and decomposes). So why drains smell - grease and food, or a dry trap - identifies the causes, which are all drainage matters. Knowing the cause points to the fix (covered next). So drains smell from grease and food build-up, a dry trap, or a blockage. This is general guidance.
How to fix it
The fix for smelly drains is drainage maintenance, not extraction cleaning. Clean the drains, gullies and grease trap: removing the grease and food build-up that causes the smell - a regular part of a kitchen deep clean and drainage maintenance (as covered in the why-floor-drains-and-gullies-belong-in-every-deep-clean page). Manage the grease trap: keeping it emptied and cleaned, since a neglected grease trap is a common odour source (as covered in the grease-trap-management page). Keep traps topped up: running water to maintain the water seals that block sewer gases.
And: clear any blockage and address drainage faults (a job for drainage or plumbing services); and avoid putting fats, oils and grease down the drains, to reduce the build-up at source (as covered in the how-fats-oils-and-grease-cost-you-at-the-drain page). So the response to smelly drains is to clean and maintain the drainage - the drains, gullies, traps and grease trap - and to keep FOG out of them. These are drainage-maintenance tasks, done as part of your kitchen cleaning and drainage upkeep (and by drainage specialists for blockages and faults) - not extraction cleaning. So how to fix it - clean the drains and grease trap - is the practical answer for a genuine drain smell: address the drainage, where the problem is. So fix a drain smell by cleaning and maintaining the drainage. This is general guidance.
The duct connection
There is one connection to the extraction worth noting. A stale, greasy smell in the kitchen can sometimes come from the extraction ductwork rather than the drains - grease decomposing in a grease-laden duct can give off a stale, unpleasant smell (as covered in the smell-of-stale-grease-and-what-it-means and smell-that-tells-you-grease-has-reached-the-duct pages). So a persistent stale grease smell isn't automatically the drains - it could be the extraction.
This is why kitchen smells can be confusing: a stale grease smell could be from grease in the drains or grease in the ducts (both are grease decomposing). So if you have a stale grease smell and assume it's the drains, you might be cleaning the drains while the real source is a grease-laden duct that needs cleaning (or vice versa). So it's worth telling which it is (covered next), rather than assuming. This is the reason a page about drain smells touches the extraction: the two can be confused, and a stale grease smell might be the duct. So the duct connection - a stale grease smell can be the extraction - is the important caveat: don't assume every kitchen grease smell is the drains; the ductwork can be the source. So a stale grease smell might be the duct, not the drains. This is general guidance.
Tell which, and act
So if you have a persistent smell, work out its source before acting - is it the drains or the duct? Where is it strongest? A smell strongest at the drains, gullies or sink points to the drainage; a smell strongest near the canopy, or that comes when the extraction runs, points to the duct. What's it like? A sewer-like or rotting-food smell suggests drains; a stale, greasy, cooking-fat smell can be either but leans toward grease (in the drains or the duct). When does it occur? A smell when water drains, or from an unused trap drying out, suggests drains; a smell tied to the extraction running suggests the duct.
So use where, what, and when to identify the source: a drainage smell (address the drains, gullies and grease trap) or a duct smell (address the extraction - a grease-laden duct needing cleaning). Then fix the right one: drainage maintenance for a drain smell, extraction cleaning for a duct smell. If it's clearly the drains, it's a drainage matter (as covered above); if it's a stale grease smell that isn't clearly the drains, have the extraction checked (it may be a grease-laden duct). Getting the source right means you fix the actual problem rather than the wrong one. So tell which, and act - drains or duct, find the source - is the takeaway: identify whether the smell is the drainage or the extraction, and address the right one. (Drainage issues are for drainage/plumbing services; extraction for your cleaner.) So find the real source and fix that one. This is general guidance.
Questions
Usually from grease and food building up in the drains, gullies, traps and grease trap, where they decompose and smell; other causes are a dry trap (letting sewer gases up) or a blockage - all drainage issues, not the extraction. Kitchen drains smell mainly because of what goes down them and builds up. Fats, oils and grease (FOG) poured or washed down the drains accumulate in the pipes, gullies, traps and grease trap, where they decompose and give off unpleasant smells - a blocked or dirty grease trap is a classic source. Food waste going down the drains rots and smells too. Other causes: a dry trap (the water seal in a trap or gully drying out, letting sewer gases up), a blockage (trapping decomposing matter), or a drainage fault. So the smell usually comes from grease and food build-up, a dry trap, or a blockage - all drainage issues, not the extraction. Grease is the biggest culprit in a commercial kitchen. The fix is drainage maintenance (cleaning the drains and grease trap, keeping traps topped up, clearing blockages), not extraction cleaning. So from grease and food build-up, or a dry trap - a drainage matter. So grease and food in the drainage. This is general guidance.
No - a drain smell is usually a drainage/grease-trap issue, separate from your ductwork; but a stale grease smell in the kitchen can sometimes be the extraction duct instead, so it's worth telling which. No - a drain smell is usually a separate issue from your extraction. Smelly drains are, in most cases, a drainage problem - grease and food building up in the drains, gullies, traps and grease trap (or a dry trap or blockage) - which is addressed by drainage maintenance, not extraction cleaning. So a genuine drain smell isn't an extraction problem. However, there's a connection worth knowing: a stale, greasy smell in the kitchen can sometimes come from the extraction ductwork rather than the drains (grease decomposing in a grease-laden duct can smell). So a persistent stale grease smell isn't automatically the drains - it could be the extraction. This is why the two can be confused. So the answer is that a drain smell is usually drainage (not extraction), but a stale grease smell might be the duct - worth telling which by where it's strongest, what it's like, and when it occurs. So no - drains are usually drainage, but a grease smell can be the duct. So mostly separate, but a grease smell can overlap. This is general guidance.
Clean the drains, gullies and grease trap (removing grease and food build-up), keep traps topped up with water, clear any blockage, and avoid putting fats and grease down the drains - drainage maintenance, done as part of your cleaning and by drainage specialists for faults. To get rid of a kitchen drain smell, address the drainage. Clean the drains, gullies and grease trap - removing the grease and food build-up that causes the smell (part of a kitchen deep clean and drainage maintenance). Manage the grease trap - keeping it emptied and cleaned (a common odour source if neglected). Keep traps topped up - running water to maintain the water seals that block sewer gases. Clear any blockage and address drainage faults (a job for drainage or plumbing services). And avoid putting fats, oils and grease down the drains, to reduce the build-up at source. So the fix is drainage maintenance - cleaning and managing the drains and grease trap, and keeping FOG out - not extraction cleaning. If, however, the smell is a stale grease smell that isn't clearly the drains, consider whether the extraction duct is the source (a grease-laden duct can smell). So clean and maintain the drainage, and keep grease out of it. So clean the drains and grease trap. This is general guidance.
Yes - a stale, greasy smell can come from grease decomposing in a grease-laden duct; so if a stale grease smell isn't clearly from the drains, the extraction could be the source, and cleaning the duct may be the fix. Yes - a kitchen smell can sometimes be the extraction rather than the drains. A stale, greasy smell can come from grease decomposing in a grease-laden extraction duct - the accumulated grease in the ductwork giving off a stale, unpleasant smell (as covered in the smell-of-stale-grease and smell-that-tells-you-grease-has-reached-the-duct pages). So while a drain smell is usually the drainage, a stale grease smell isn't automatically the drains - it could be the ductwork. This matters because you might clean the drains while the real source is a grease-laden duct (or vice versa). So if you have a stale grease smell and it isn't clearly coming from the drains (strongest near the canopy, or when the extraction runs), consider the extraction as the source - and have it checked and cleaned (a grease-laden duct needs cleaning to TR19 Grease). So yes - a stale grease smell can be the duct; tell which by where it's strongest and when it occurs. So yes; a grease-laden duct can smell. This is general guidance.
By where it's strongest (drains/sink vs canopy), what it's like (sewer/rotting-food suggests drains; stale grease can be either), and when it occurs (when water drains suggests drains; when the extraction runs suggests the duct). To tell whether a persistent kitchen smell is the drains or the extraction duct, consider three things. Where is it strongest? A smell strongest at the drains, gullies or sink points to the drainage; a smell strongest near the canopy, or that comes when the extraction runs, points to the duct. What's it like? A sewer-like or rotting-food smell suggests drains; a stale, greasy, cooking-fat smell can be either but is grease (in the drains or the duct). When does it occur? A smell when water drains, or from an unused trap drying out, suggests drains; a smell tied to the extraction running suggests the duct. So use where, what and when to identify the source - a drainage smell or a duct smell - and then address the right one (drainage maintenance for a drain smell; extraction cleaning for a duct smell). If it's unclear, you can address the drains first (the more common cause) and, if the smell persists, have the extraction checked. So tell by where it's strongest, what it's like, and when it occurs. So by location, character and timing. This is general guidance.
No - a genuine drain smell is fixed by drainage maintenance (cleaning the drains and grease trap), not extraction cleaning; extraction cleaning only helps if the smell is actually from a grease-laden duct, not the drains. No - extraction cleaning doesn't fix a genuine drain smell. A drain smell comes from the drainage system (grease and food building up in the drains, gullies, traps and grease trap, or a dry trap or blockage), so it's fixed by drainage maintenance - cleaning the drains and grease trap, keeping traps topped up, clearing blockages - not by cleaning the extraction ductwork. So if the smell is genuinely from the drains, extraction cleaning won't address it. Extraction cleaning only helps with a smell if the smell is actually coming from the extraction (a stale grease smell from a grease-laden duct) rather than the drains. So the key is to identify the source first: if it's the drains, clean and maintain the drainage; if it's the duct (a stale grease smell not clearly from the drains), clean the extraction. Cleaning the wrong one won't fix the smell. So no - a drain smell needs drainage maintenance, not extraction cleaning. So no; only if the smell is actually the duct. This is general guidance.
A drain smell is usually a drainage matter - but a stale grease smell can be a grease-laden duct; if the source isn't clearly the drains, we can check and clean the extraction to TR19 Grease, removing decomposing grease that may be the real cause. Ask us to check your extraction if a grease smell persists. This is general guidance.
