Grease Dripping From the Kitchen Hood Onto the Cooking Line: Where It Comes From and Who Fixes It

Pictured above: grease runs and hanging drips along the lower edge of a hood panel, below the filter frame, on one of BC Air’s projects (Old Chang Kee, Aljunied). This is a photo from our own work, reused here because it shows what a hood looks like when grease has stopped draining where it was meant to and has started to travel on its own.

It is mid-service and a bead of brown grease forms on the lower edge of the hood, swells, and drops onto the pass, the chopping board or the hot plate under it. A minute later another one follows. The cook wipes it with a cloth and carries on, because the orders are coming in, and by the end of the night it has become a habit.

A hood that drips is telling you that grease is leaving the path it was designed to take. Grease is meant to be caught by the filters, run down into the gutter, and be emptied or cleaned out on a routine. Every drip means one of those steps has failed somewhere upstream of the drip. The useful question is not “how do I stop the drip” but “which step failed”, because the answer decides who fixes it and how fast.

First, the part that cannot wait for the next service

Grease landing on food is a hygiene problem. Grease landing on a flame or a hot surface is a fire problem. Either one is a reason to act today, not a reason to note it in the log and carry on.

• If drips are landing on an open flame, a fryer or a hot plate, stop using that position until it is dealt with. A flare-up under a hood is how a kitchen fire starts, and we explain what happens next in how a grease fire travels up kitchen ductwork.
• Move food, utensils and prep boards out from under the drip line, and wipe the surface below with a degreaser before the next service.
• Do not stick tape, foil or sealant on a hood to catch or hide a drip. It hides the symptom, adds a fuel layer, and makes the real fault harder for the next person to find.
• Do not hose or flood the hood with water to wash it down while the system is live. Wet grease and electrical fittings in a hood do not mix.

Where a hood drip actually comes from

From the floor, every drip looks the same. In practice there are about six sources, and they leave different clues. Stand under the hood after a service, with the kitchen cold and the system off, and look at where the grease is and where it is not.

1. The grease gutter or cup is full

Filters drain into a gutter at the bottom, and many hoods have a cup that collects what the gutter carries. When it is full, it has nowhere left to put what the filters send down, and the grease spills over the lip. We cover the daily habit in the daily kitchen routine for the exhaust system. The clue is that the drip comes from the lowest edge of the hood, just under the filters, and gets worse towards the end of a long service.

2. A filter is the wrong way round, not seated, or missing

A baffle filter is built to drain in one direction, towards the gutter. Put it back upside down or turned and the grease runs to the wrong edge, or gets thrown past the gutter altogether. A filter that does not sit properly in its runners leaves a gap, and grease finds the gap. The clue: it started the morning after a filter wash or a professional clean, and one panel in the bank sits crooked or proud of its neighbours. See what to check after a cleaning night.

3. A filter or the gutter edge is bent

A dropped filter, or one levered out of a tight frame, can have a crushed bottom edge. The channels can no longer carry the grease to the gutter, and it goes back into the airflow or runs off the side. A bent gutter lip does the same. The clue is a drip in one spot that does not move, under one particular panel. If that panel is damaged, treat it as out of service. We explain how to judge that, and what to measure, in when a baffle filter is damaged.

4. The hood surfaces are loaded with grease

This is the one in the photo. Grease does not only collect in the filters. It film-coats the inside walls and the underside of the hood, and over months it turns tacky and heavy. When the hood is hot, it softens and runs, and it runs towards the lowest edge. The clue is drips that are worst at the end of service when the hood is hot, with runs and streaks visible on the inner panels, and a drip that comes from wherever the grease finds an edge, not from a fixed point. This is a cleaning job, not a repair job, and the answer is in kitchen exhaust cleaning. If it keeps happening between cleans, the interval is too long for what the kitchen cooks. We cover that in how often to clean a commercial kitchen exhaust.

5. A seam, joint or panel is letting it through

Hoods are fabricated from sheet metal. Where panels join, a seam can open with age, heat and repeated cleaning, and grease that should have stayed inside the hood weeps through. A similar leak can come from a joint where the hood meets the duct collar. The clue is a drip that appears on the outside of the hood or from a joint line, sometimes with a stain trail leading to it, and sometimes appearing even when the filters and gutter are clean. This needs a repair rather than a wipe-down, and the repair has to be done in metal, not with a smear of sealant. Damage and rust are covered in damaged, leaking or rusted kitchen hood: repair or replace.

6. It is not grease at all

Steam condenses on cool metal, and a hood in an air-conditioned kitchen can sweat. Water also gets in after heavy rain. If the drip is clear or only faintly brown, runs from a duct or the collar rather than the filter edge, and is worst in humid or wet weather, read kitchen exhaust duct condensation and water at the hood after heavy rain before assuming grease.

A five-minute check you can do yourself

Do this when the kitchen is cold and the system is off and isolated, never while the fan is running or anything is hot.

1. Look at the gutter and cup under the filters. Is it full, or crusted over so that it cannot drain?
2. Look at each filter in the bank. Are they all the same type, all the same way round, all seated, none bent? If one differs from its neighbours, that is your first suspect.
3. Run a gloved finger along the lower edge of the hood and the inside walls you can reach. Tacky, wet or streaked means surface build-up.
4. Look for a stain trail on the outside of the hood leading back to a seam or corner.
5. Note the time pattern. Does it drip early in service or late? Only after rain? Only since the last filter wash or professional clean?

That last point is the most useful single piece of information you can give a contractor. A drip that started the morning after a wash points at filters. One that builds across a service points at a full gutter or a hot, loaded hood. One that follows the weather points at water.

What each source means for who fixes it

• Gutter and cup, filters seated and the right way round: the kitchen’s own routine, done earlier and more consistently.
• Bent filter or gutter lip: a replacement or a repair to the hood. Send photographs and measurements.
• Loaded hood surfaces: a professional clean of the hood, filters and, if the grease has also built up behind them, the plenum and duct.
• Open seam or joint: a repair by a fabricator who can work in the same metal. We fabricate ductwork in-house, which is why this is a job we can look at rather than pass on.
• Water, not grease: a different investigation, and a different contractor may be involved if the cause is the building, not the kitchen.

What to send us

• Where the drip lands: which part of the line, and what is cooked there.
• Photographs of the hood from the front, the lowest edge, the gutter or cup, and the spot you think it comes from.
• When it started, and what changed just before: a filter wash, a professional clean, a new appliance, a change in menu or hours.
• Whether it follows the weather or follows the cooking.
• When the filters, hood, duct and fan were last cleaned, if you know.
• Whether the filters are baffle or mesh, if you are sure.

Hood dripping onto the line? WhatsApp BC Air on 8989 2833 with the details above. We are on 24/7 standby, and scope and pricing follow an assessment. We look at what is actually causing the drip before quoting, because a hood that drips because of a full gutter and one that drips because of an open seam are different jobs.

Related reading: what sits behind the baffle filters · the daily kitchen routine for the exhaust system · when a baffle filter is damaged