Do Grease Traps Smell? Causes, Solutions & How to Stop Grease Trap Odours

Grease traps are found in all commercial kitchens and settings where fats, oils and grease (FOGs) are produced. Sometimes, they will begin to smell pretty bad, which is not good for your business. The foul odours could be down to several reasons, and this guide from the experts at Aqua Mundus will answer why grease traps smell and how to tackle the issue properly.

What Are Grease Traps?

Do Grease Traps Really Smell?

Why Does My Grease Trap Smell

5 Main Causes

Is Grease Trap Smell Toxic?

How to Prevent Grease Trap Smells

Signs Your Trap Needs Cleaning

How Often Should They Be Cleaned?

How to Clean a Grease Trap

How Much Does It Cost?

Grease traps act as a system that intercepts and separates fats, oils and grease (FOGs) from wastewater before they enter the sewer system. Multiple types of grease traps are available to meet the specific demands of commercial kitchens, but all have the same goal of separating harmful substances from blocking sewers and causing environmental harm.

Grease traps are found in all commercial kitchens and settings where fats, oils and grease (FOGs) are produced. Sometimes, they will begin to smell pretty bad, which is not good for your business. The foul odours could be down to several reasons, and this guide from the experts at Aqua Mundus will answer why grease traps smell and how to tackle the issue properly.

In short, yes – grease traps can smell quite bad on occasion, but that doesn’t mean they have to smell bad all the time. Noticeable smells generally occur when the grease trap isn’t clean or hasn’t been maintained properly.

If left to develop a large volume of collected FOG, a grease trap can smell very bad. One of the main foul odours you’ll notice from a grease trap is a rotten egg smell, caused by hydrogen sulfide gas, produced when bacteria breaks down decomposing FOGs. Other nasty odours will include sour and rancid smells from decomposing food, and many often mistake a grease trap smell to that of sewage. If you continue to notice uncomfortable, rancid and egg or sewage like odours around your restaurant sink areas, it’s a sign you need to inspect your grease trap. 

Grease traps collect food particles, oils and organic matter, which will decompose and release unpleasant sulphur-based gases and other fatty acid gases. Reasons a grease trap can smell toxic include:

Let’s look at a few specific examples of what makes grease traps smell offensive in more detail.

Despite all efforts, food waste particles and sediment will get into your wastewater and will be captured by your grease trap. Once trapped, they will begin to decompose and release foul-smelling gases. This can build up and completely block your trap, almost guaranteeing foul grease trap smells.

Certain types of bacteria thrive in the stagnant, oxygen-starved environment that develops in an under-maintained grease trap. As these bacteria break down the waste, they release strong odours that will eventually find their way out of your grease trap and into your kitchen and premises.

Grease traps need regular cleaning and maintenance. Anything less will result in excessive food waste and FOG buildup that ultimately enables odours to develop and worsen. Worn-out seals let odours escape and blocked traps make it easy for foul gases to back up through pipework. 

Grease traps are typically installed near sinks and drainage areas, and if the smell is emanating from these areas, then the grease trap is the likely culprit. Other common signs include slow drainage, visible grease around the trap cover, or bubbling sounds from the pipework. Lifting the lid of the trap carefully can confirm if there’s a thick layer of sludge or standing water giving off a foul smell.

We often get asked why grease traps smell, so here’s the top 5 main reasons why. 

Over time, food particles and FOGs will accumulate in the trap and solidify. These will decompose and break down by microorganisms which release sulphuric gases, resulting in rancid smells. Without timely removal and pumping, the buildup can block water flow and cause foul gases to escape through drains. 

Why have so many FOGs lingered in the trap? Because you’re not cleaning and maintaining it when you should! It’s recommended you do a deep clean of your grease trap at least every one to three months, or more, depending on usage.

Lack of cleaning is the most common cause of bad grease trap smells, and without a schedule employed will lead to rotting organic matter releasing odours that can spread fast. 

Warm, moist environments inside the trap and surrounding areas promote bacterial growth. The more bacteria feeding on the trapped waste will result in more methane and hydrogen sulphide gases, both known for their strong, unpleasant odour. 

Sometimes, bad smells from a grease trap can be caused by faulty seals or other plumbing issues. Worn gaskets, cracked covers or poorly sealed joints can allow gases to escape, and damaged pipework can also cause wastewater to stagnate, amplifying grease trap smells.

If you have a grease trap that’s too small for your kitchen, volume of FOGs produced and your water flow rates, it will fill up too quickly and produce foul odours. Frequent overloading also reduces efficiency and increases stagnant water inside the trap itself, creating the perfect conditions for bacteria growth and unpleasant smells. To discover the perfect sized grease trap for your premises, use our handy size calculator. 

Many believe that grease traps smell bad all the time, but this is simply not true. By properly maintaining the system, strong odours shouldn’t be a worry. Also, many believe that simply pouring down chemicals or deodorisers can solve the problem, but this only masks the smells temporarily and doesn’t address the buildup of decomposing waste that causes them.

Toxic smells can fall under the government’s classification of ‘nuisance smells’, which are unreasonable odours that substantially interfere with the use or enjoyment of a home or other premises, and can also injure or likely to injure health. 

Hydrogen sulphide, methane and ammonia are all foul gases that can be produced from a grease trap. These gases can negatively affect staff and customers, causing:

It’s vital to ensure grease traps and the surrounding kitchen extractor and ventilation systems are regularly maintained and cleaned to counteract foul smells. 

It might be stating the obvious, but hands-down the best preventative method is establishing and sticking to a regular cleaning and maintenance routine. Daily cleaning should be part of kitchen breakdown procedures, and full deep cleans are recommended every 1-3 months, or when the trap is 25% full. Grease trap servicing should be done either monthly or quarterly, and all accumulated FOGs must be removed and disposed of responsibly. 

Using the right cleaning agents for drain treatment and grease trap maintenance is essential, as using incompatible solutions or harsh chemicals can damage the trap and harm beneficial bacteria. Using enzyme-based products and biological cleaners can also improve the performance of a grease trap, breaking down FOG safely without corroding or damaging the trap itself. 

Good airflow helps disperse smells and prevents gas buildup. Make sure the trap and kitchen area have adequate ventilation and that any exhaust systems are working efficiently. Problems like poor ventilation is just one of the issues the team at Aqua Mundus can help with. 

Just because a grease trap separates food waste from the wastewater, it doesn’t just mean it can handle excessive and unnecessary amounts of food waste. Any pot washers or waiting staff should scrape all wasted food off plates before they go into sinks or wash machines. 

Regular inspections by trained professionals can catch early signs of leaks, blockages and worn components. Professional services also ensure full waste removal, proper disposal and compliance with local waste regulations, keeping your grease trap system odour-free and efficient. 

To avoid foul grease trap smells, you’ll need to clean it. If you notice strong smells like rotting eggs, notice your sinks are draining slowly, there’s significant grease build up on the trap’s lid, or gurgling sounds coming from sewage pipes, get the rubber gloves on and get cleaning!

Regular grease trap cleaning is essential to prevent blockages, foul odours and costly plumbing issues. While exact schedules can vary depending on usage and local regulations, the following guidelines are widely accepted across the industry and align with standard best practices.

If you’re looking at how to stop grease trap smell then you need to know how to clean a grease trap. Here’s a quick breakdown, but for more details read our step-by-step cleaning guide.

Commercial grease traps and interceptors should always be cleaned by a professional to ensure compliance and safe waste disposal. 

The cost of grease trap cleaning can vary depending on certain factors, including:

Do grease traps smell? Yes, but only if you let them. If you need to know how to stop grease trap smells and ensure stench-free systems that work efficiently and are compliant, choose Aqua Mundus and our range of tailored grease trap services, from maintenance and cleaning to keep smells and other issues at bay, as well as full installation of above ground and underground grease traps, as well as a range of other products. We’re here to support many industries with grease traps nationwide with accredited solutions and expert support. 

Speak to an expert at Aqua Mundus today for any assistance, regular or urgent, for your grease trap systems.