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Hidden dangers in clogged grease traps

Written by Eamonn Ryan

Neglecting to clean grease traps can result in compromised hygiene, an issue post-Covid-19 that is of the highest priority. Grease traps require regular cleaning and the proper disposal of waste in order to be compliant.

This is something frequently neglected by a host of businesses – restaurants, hotels, car washes and petrol garages homes. All the cooking fat, make-up, hair, car grease and oil goes down the drain and into the sewer to form fatbergs. Fatbergs build up on sewer roofs like mushy stalactites. In one well-reported case eight years ago in London, it took a team of municipal worker three weeks to defeat a toxic 15-tonne ball of congealed fat the size of a bus that came close to turning parts of the London borough of Kingston upon Thames into a cesspit.

“The worst is when it gets as far as the waste treatment plant at which point it starts adding massive maintenance cost to the water treatment. This requires a massive education drive. It is another example where enforcement is not taking place,” says Brendan Reynolds, executive director of IOPSA.

This is a rare instance of plumbing where the plumber can be proactive by solving blockages before being called out. In the profession, the majority of services are heavily tied to reactive problem-solving. Grease traps are such a line of work. “Few restaurant owners even think of their grease trap once it’s installed (if they even have one) and it would be almost guaranteed work for a plumber to sign up such customers for regular maintenance contracts. This can be healthy for the environment, as well as highly profitable for the profession,” says Reynolds.

He says that even where a grease trap call-out is reactive, there are some steps a plumber can take to develop regular contractual work:

“If something needs to be corrected, this is the chance to make it right and keep this customer.

  • Send out a friendly reminder three to six months after service.
  • Remind the customer that their grease trap may require a service again – it keeps the plumber’s business top of mind, as well as accomplishing a civic duty.
  • Send an annual holiday card or spring-cleaning reminder.”

The plumbing opportunity in grease traps

“Grease trap cleaning can typically fall behind for two reasons: Firstly, these necessary but unsightly devices are out of sight, and secondly, the task of removing trapped grease and fat is unpleasant. Grease traps are a necessity in all types of eateries, as they prevent FOGs (fats, oils and greases) from entering the drainage system, with on average a single stage grease trap retaining 50-90% of the FOG that enters the trap. This has to be manually disposed of, though automation of this is becoming more common among eateries that can afford the more sophisticated traps,” says Reynolds.

Grease traps that aren’t regularly cleaned can become a health hazard to staff and patrons. Traps full of FOGs become a beacon for pests such as flies, cockroaches and rodents, which is why regular cleaning is essential. They also emanate an unpleasant odour – something highly off-putting for diners. Traps that have a substantial build-up of fatty deposits are difficult to clean, become inefficient as a result of blockages – but more importantly it is inadvertently illegal. Many restaurateurs are unaware that waste from their grease traps falls under ‘controlled waste’ legislation when it also contains rotted food solids (called ‘brown grease’). This means that it can only be removed by a registered waste carrier under strict waste removal and disposal regulations, shielding customers from government fines or the possibility of putting the restaurant’s whole operation at risk.

Consequently, grease traps require regular cleaning and the proper disposal of waste in order to be compliant.

The grease trap

Grease traps have been used since Victorian days: Nathaniel Whiting obtained the first patent in the late 1800s. They can be made from many different materials, such as stainless steel, plastics, concrete and cast iron. They range from 35ℓ capacity to 45 000ℓ and greater. They can be located above ground, below ground, inside the kitchen or outside the building.

“Restaurant and foodservice kitchens produce waste grease commensurate with the number of meals they serve a day – grease which is present in the drain lines from various sinks, dishwashers and cooking equipment. If not removed, the grease can clump and cause blockage and back-up in the sewer,” says Reynolds.

For this reason, municipalities require commercial kitchen operations to use some type of interceptor device to collect grease before it enters sewers. Municipalities also have inspector programmes to ensure grease traps are regularly maintained. Roberto Berti, technical director of Herbish Drainage Systems, lists two frequent problems he experiences with grease traps: “Often, for price reasons, too small a grease trap is installed, as the traps are a grudge purchase for many businesses; secondly, once installed they aren’t frequently looked at. In both cases they can become useless: if too small it fails to separate the FOGs; and if not maintained they become blocked and sometimes back up.

“A full grease trap does not stop any FOG from entering the sanitary sewer system. The emptied contents or ‘brown grease’ is often hazardous waste.” There is an exact formula for calculating how large a grease trap a restaurant needs, based on the number of meals served and the type of food – as chicken dishes produce more grease than other meats. Unfortunately, providing a large tank for the effluent to stand also means that food waste has time to settle to the bottom of the tank, reducing available volume and adding to clean-out problems. Also, rotting food contained within an interceptor breaks down, producing toxic waste (such as sulphur gases) – hydrogen sulphide combines with the water present to create sulphuric acid. Berti says that sulphuric acid attacks mild steel and concrete materials, resulting in the rotting smell, and damaging the unit.

He explains that the size of a grease trap is dictated by the amount of grease water going through it: if 1 000ℓ of water is discharged from a kitchen, it sits in the grease pump for six minutes for the grease to separate out, which means a 6 000ℓ trap is required.

“The law (National Building Regulations SANS 10 400 P), says you need a grease trap, but many older buildings never had one prior to the regulation and when an inspector threatens to shut him down, he only then calls in a plumber to put in the cheapest possible grease trap (a 300 X 300 X 300mm) which is just a glorified solids catcher, and installed in line with two big pot sinks which is something the designers of kitchens often don’t think about,” says Berti.

A special problem is the food halls of shopping malls where food preparation is concentrated and there is limited space for traps. Berti explains that if the grease trap is too far from the kitchen, the risk exists that the pipes may already become blocked before the grease ever reaches the trap. However, in the case of a new development the wet services engineer would certainly provide for a trap: “They know about grease traps and where to put it, and they often come to us for advice.”

The need for professional advice from plumbers, manufacturers or wet services engineers is demonstrated by Marley’s fact sheet on its Marley Endura grease trap, where it states: “Proper installation of a grease trap is critical to its efficient operation. Even the best designed grease trap will not operate efficiently unless it is installed correctly.” It continues that placement should allow the cover to be easily removed for cleaning, as well as a minimum clearance to allow removal of the internal baffles for a complete clear-out.

“Installations requiring long runs of pipe (exceeding 7.5m) are to be avoided. This precaution will reduce the possibility of the pipeline becoming clogged with grease before reaching the grease trap. Grease waste lines should be piped at a minimum slope of 6mm per 304mm to maintain flow in the drain line.” The company Grease Traps was one of the first plumbing companies to recognise the potential for grease trap cleaning in South Africa in the 90s and found the business so lucrative that it later got into grease trap manufacture, and is currently expanding its operation. Recognising that grease traps are a grudge purchase, and price the senior issue, the company introduced a locally manufactured product at much lower costs. However, it importantly maintained a quality standard that the South African market was accustomed to, expanding into the market by reducing the average market cost of grease trap equipment.

Enforcement is lacking

SANS 10252-2, as referenced by National Building Regulations (SANS 10400 P), defines the minimum requirements for grease traps which must be installed in the drains of all catering and food processing businesses to prevent pollution of the sewers. Ricky Chatburn, Managing Director – ACO Systems: South Africa and sub-Saharan Africa, says: “The enforcement of the regulations is lacking. It is adhered to in the design and approval phase, but the challenge comes when installation takes place: there is the risk of substitution to alternative non-compliant products. The best advice here is to always stick to the specification, as using alternatives is a grey area open for abuse.”

On the issue of whether grease trap maintenance is done with sufficient vigour, plumbers could supplement their business by arguing to potential customers that a grease trap is one of the kitchen’s most valuable assets. “Keeping it properly maintained prevents a whole host of issues, from unpleasant odours to shut-downs and even fines. Issues with grease trap maintenance are the lack of experienced service technicians, the knowledge of when (how often) and how to clean the grease trap properly, as well as management. Staff need to be probably trained on this aspect, this entails maintenance intervals, cleaning procedure and safe disposal of waste,” says Chatburn.

“The role of plumbers in terms of grease traps is to understand the system, when to have a grease trap installed and its correct sizing,” he added.

How grease traps work:

When the outflow from the kitchen sink enters the grease trap, the solid food particles sink to the bottom, while lighter grease and oil floats to the top. The relatively grease-free water is then fed into the normal septic system. The food solids at the bottom and floating oil and grease must be periodically removed in a manner similar to septic tank pumping. A traditional grease trap is not a food disposal unit. Unfinished food must be scraped into the garbage or food recycling bin before entering the sink or dishwasher. Because it has been in the trap for some time, grease thus collected will be contaminated and is unsuitable for further use. This type of grease is called brown grease.

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