Grease trap cleaning is one of the most important things you can do to keep your drainage system running properly. If fat and oil are allowed to build up unchecked, you are looking at blocked pipes, foul smells, slow drainage, and repair bills that could have been avoided entirely. Whether you manage a commercial kitchen, run a restaurant, or simply want to protect your home drainage, this guide covers everything you need to know: how grease traps work, how to clean them, how often to do it, and when it makes sense to call in a professional.

What Is A Grease Trap And Why Is It Important?

A grease trap, also called a grease arrestor or grease pit, is a plumbing device designed to intercept fats, oils, and grease before they enter your main drainage system. You will find them most commonly in commercial kitchens, restaurants, food production facilities, and some domestic properties.

The way it works is straightforward. Wastewater slows down as it flows through the trap, allowing grease to rise to the surface while solid waste sinks to the bottom. The cleaner water in the middle then continues through the drain grease trap and into the wider drainage system. This separation process is what protects your pipes from the sticky, hardening residue that causes so many drainage problems. 

Without regular grease pit cleaning and grease arrestor cleaning, the trap fills up, loses its effectiveness, and grease starts making its way into your pipes. At that point, you are no longer preventing a problem; you are managing one. 

What Happens When Grease Builds Up In Your Drains

When grease is not removed regularly, it does not just sit harmlessly in the trap. It hardens, sticks to pipe walls, and begins to accumulate layer by layer. Over time, this narrows the pipe and restricts water flow.

The most common consequence is fat in drains that traps food particles and solidifies into a dense blockage. You will usually notice the warning signs before a full blockage develops: slow drainage, gurgling sounds from pipes, a persistent unpleasant smell, or water backing up in sinks. Left unchecked, these issues escalate quickly.

At Absolute Plumbing Ltd, we regularly attend callouts in London where grease in pipes has been building for months without anyone realising. By that stage, the blockage has often spread well beyond the trap itself, which means more time, more disruption, and higher costs. Regular cleaning of grease traps is far cheaper than the alternative.

How To Clean A Grease Trap (Step By Step)

Cleaning a grease trap is manageable on smaller domestic systems, but the process is the same regardless of size. Here is how to clean a grease trap safely and thoroughly:

1. Turn off the water supply: Stop any water from entering the system before you start work.

2. Remove the lid carefully: Some lids are heavy or sealed tightly. Take your time and do not force it.

3. Scoop out the floating grease: This is the most important part of cleaning a grease trap. Remove the top layer of solidified fat and waste and dispose of it responsibly, never down a drain.

4. Scrape down the internal surfaces: Use a scraper to remove hardened residue from the sides, baffles, and any internal components.

5. Apply a grease trap cleaner: A suitable grease trap cleaner or fat trap cleaner will break down remaining residue and help deodorise the system.

6. Reassemble and test: Replace the lid securely, then run water through the system to confirm it is draining correctly.

Always wear gloves and eye protection when you clean a grease trap, and make sure waste is disposed of in line with your local council’s guidelines. In London, this typically means bagging solid waste for general waste collection rather than putting anything down the drain.

Different Types Of Grease Trap Cleaning You Should Know

How to clean grease traps varies depending on the size and setup of your system. Here is a breakdown of the most common types:

Grease Pit Cleaning

Grease pit cleaning applies to large underground systems typically found in commercial kitchens and food production facilities. These handle high volumes of waste and require intensive servicing, usually on a planned schedule due to the scale of the work involved.

Grease Tank Cleaning

Grease tank cleaning is used for larger above-ground storage systems that collect fats, oils, and grease before disposal. Without regular grease tank cleaning, these systems can overflow or develop heavy internal buildup that becomes difficult to shift.

Grease Arrestor Cleaning

Grease arrestor cleaning covers smaller interceptor units, common in both commercial and domestic settings. These sit inline with your drainage and need regular attention to stay effective. Because they are smaller, they fill up faster than people often expect.

Grease Trap Clean Out

Grease trap clean out is the corrective service called for when a system is already showing signs of trouble, such as slow drainage, bad smells, or an overflow. It removes accumulated waste and restores normal flow. If you find yourself needing a clean out regularly, it is usually a sign that your routine maintenance schedule needs adjusting.

How Often Should You Clean A Grease Trap?

The right frequency depends on how heavily your system is used. As a general guide:

• Light use (small domestic or low-traffic commercial): Every 2 to 3 months
• Moderate use (mid-size commercial kitchen or cafe): Every 1 to 2 months
• Heavy commercial use (busy restaurant, takeaway, or food production): Monthly, or more frequently in peak periods

The signs that you need to clean grease traps sooner than scheduled are hard to miss: strong or lingering odours, slower than usual drainage, visible grease buildup around the trap, or any overflow or backup. Do not wait for things to get worse.

If cleaning is delayed, grease does not stay put. It hardens and migrates further into the drainage system, turning what would have been a routine service into a much more involved job. In our experience serving commercial clients across London, the businesses that stick to a regular schedule almost never face emergency callouts for grease-related blockages.

Can You Clean A Grease Trap Yourself, or Should You Call A Professional?

For small domestic systems with light, manageable buildup, a basic DIY approach to cleaning grease traps is perfectly reasonable. Keeping on top of it between professional services can prevent minor accumulation from becoming a bigger problem.

That said, there are situations where DIY is not the right call. If the buildup is heavy, if blockages keep coming back, or if smells persist even after you have cleaned the trap, attempting to deal with it yourself can push grease further into the pipework and make things worse. In commercial settings, there is also a compliance dimension: waste from grease trap clean outs must be disposed of correctly, and improper handling can create issues with local authority inspections.

Professional grease trap cleaning ensures the system is fully cleared rather than just surface cleaned, and any underlying drainage issues are identified before they develop further. Absolute Plumbing Ltd provides expert grease trap cleaning across London for both domestic and commercial properties. We are Gas Safe registered, verified on Checkatrade and TrustATrader, and our engineers are experienced in all types of drainage systems.

How to Prevent Grease Build-Up In Pipes And Drains

Prevention is always easier than dealing with a blockage. Here are the habits that make the biggest difference when it comes to keeping grease in pipes and fat in drains under control:

• Never pour fats, oils, or cooking grease down the sink, even in small amounts or diluted with hot water
• Wipe pans, trays, and cookware with a paper towel before washing to remove residue before it reaches the drain
• Use sink strainers to catch food particles and empty them regularly
• Collect used cooking oil in a sealed container and dispose of it in your household waste or at a local recycling point
• In commercial kitchens, make grease disposal part of a written daily routine so it does not depend on any one person remembering
• Set a regular maintenance schedule for grease trap cleaning and stick to it, rather than waiting for problems to appear

When To Book Professional Grease Trap Cleaning

Some situations call for a professional rather than a routine clean. You should book professional grease trap cleaning if you notice any of the following:

• Blockages that keep returning despite regular cleaning
• Strong or persistent odours that do not clear after a clean
• Drainage that is consistently slow across multiple sinks or outlets
• Any overflow or backup from the trap itself
• An upcoming environmental health inspection or tenancy check

For businesses in London, compliance is a particularly important consideration. Commercial food premises are required to maintain effective grease management systems under the Environmental Protection Act 1990 and Water Industry Act 1991, and failing to do so can result in enforcement action from the local authority or Thames Water.

Absolute Plumbing Ltd provides professional grease trap cleaning for homes and businesses across London. Whether you are dealing with a recurring blockage, persistent odours, or simply want to get your maintenance back on track, our team will clear the system properly, identify any underlying issues, and advise on the right cleaning schedule going forward. We are available on 07341 547739.

Frequently Asked Questions About Grease Trap Cleaning

If you still have questions about grease trap cleaning, you are not alone. Below are the questions our London drainage team gets asked most often, along with straightforward answers to help you make the right decisions for your system.

How often should a grease trap be cleaned?

For most domestic systems, every 2 to 3 months is sufficient. Commercial kitchens should aim for monthly cleaning, or every 1 to 2 months for moderate use. The busier the kitchen, the more frequently the trap needs attention.

What happens if you do not clean a grease trap?

Grease hardens and migrates into the wider drainage system, causing blockages, slow drainage, bad smells, and eventually pipe damage. What starts as a maintenance issue can quickly become a costly emergency repair.

Can I clean a grease trap myself?

On small domestic systems with light buildup, yes. For commercial systems, heavily blocked traps, or any situation involving persistent odours or repeat blockages, professional cleaning is the safer and more effective option.

What is the difference between a grease trap and a grease arrestor?

They serve the same purpose. Grease arrestor is simply another term for a grease trap, often used to describe smaller inline units in commercial or domestic drainage systems.

Is grease trap cleaning a legal requirement for businesses in the UK?

Commercial food premises have a legal duty to prevent fats, oils, and grease from entering the public sewer under the Water Industry Act 1991. Grease traps are the standard way to meet this requirement, and they must be properly maintained to remain compliant.

How do I know if my grease trap needs cleaning?

The most common signs are slow drainage, bad smells coming from drains or the trap itself, visible grease buildup around the unit, or water backing up in sinks. If you notice any of these, arrange a clean as soon as possible.

Don’t Let Grease Take Over Your Drains 

Regular grease trap cleaning is what stands between a smoothly running drainage system and an expensive, disruptive blockage. The longer it is left, the harder and more costly the problem becomes to fix.

Knowing how to clean a grease trap helps with basic maintenance, but professional servicing is what keeps the system performing reliably over the long term, especially in commercial settings where the volume of grease is high and compliance matters.

If you are seeing slow drainage, recurring smells, or it has simply been too long since your last service, contact Absolute Plumbing Ltd today for professional grease trap cleaning. Our London drainage team will clear your system properly, identify any underlying issues, and make sure you have the right maintenance plan in place so the problem does not come back. Call us on 07341 547739 or get in touch via absoluteplumbingltd.co.uk.