Guide
Guide to choosing a grease trap in 2026 – what to look for regarding resource efficiency and regulations
Every week, thousands of grease traps in Danish restaurants, canteens, and commercial kitchens are emptied and cleaned. This costs time and money – and often it happens too rarely or too frequently because the cause of the rapid clogging has not been identified.
Introduktion
The problem is often not the separator itself, but the greasy wastewater that flows into it. Grease binds to organic material and forms clumps that settle in the separator and reduce its capacity. The faster the grease clumps, the more frequently the unit needs to be emptied – typically every 14 days in a busy kitchen. Traditional solutions often focus on more frequent emptying or harsher cleaning, but they do not solve the root cause of grease blockages.
This guide explains what to look for when choosing a grease trap in 2026: types, legal requirements, electrostatic discharge technology, and correct sizing – as well as how new technology can significantly extend emptying intervals without compromising the purification effect.
What is a grease trap, and what types are there?
A grease trap separates grease and oil from wastewater to protect watercourses and sewers from grease blockages. The most common solutions are gravity-based separators and mechanical separators, each suitable for different applications and operating conditions.
How do the different types of grease traps work?
Grease traps utilize density differences: gravitational separators allow grease to float to the surface for collection, while mechanical separators use automated mechanisms or scrapers to enhance separation. Efficiency depends on design, load, and application.
Sludge trap: All grease traps in accordance with DS 432:2020 and DS/EN 1825-2 must have a sludge trap – a pre-chamber that retains solid particles before the water passes through the grease trap itself. The sludge trap must be emptied regularly and is a mandatory part of the approved installation.
What are the advantages and disadvantages of the different types?
Gravity separators are often cheaper to acquire and simpler to maintain, but can be less effective at high grease concentrations. Mechanical separators handle larger quantities and varied grease content, but require more maintenance and have higher installation costs. Consider efficiency, maintenance needs, and budget when choosing.
Which legal requirements and standards apply to grease traps?
Clear requirements regulate the use of grease traps to protect the aquatic environment.
Which standards and certifications must a grease trap comply with?
To comply with regulations, a grease trap must have relevant certification and documentation – typically test data demonstrating efficiency and environmental impact. The key standards are:
- DS/EN 1825-1 and DS/EN 1825-2: European standards for grease traps for use in food establishments
- DS 432:2020: Danish standard for drainage installations – includes requirements for sizing and grease traps
- Pipe Centre Guideline 005 (Technological Institute): Practical guide for installation and maintenance of grease traps
Have the documentation ready for inspection.
What do the regulations say about the grease content in wastewater?
The Danish Environmental Protection Agency's guideline (no. 2, 2006) recommends that the grease content in discharged wastewater does not exceed 50 mg/l. Municipalities administer and implement these requirements locally, and conditions may vary. Always check the local wastewater permits for your business.
How do you choose the right grease trap for your industry?
The choice depends on industry, grease load, flow, and operating conditions. Begin by mapping actual wastewater volumes and grease content before making a decision.
Which industry-specific solutions are available?
Restaurants often require high-capacity solutions for cooking grease. Catering companies and canteens must size their systems based on varying loads, while industrial plants require specially designed separators for varied oil and grease content.
How is the grease trap correctly sized?
Correct sizing is crucial: calculate capacity based on expected wastewater volume (specified in litres per second), grease content, and maximum load situations. An undersized unit results in inefficient treatment and the risk of violating discharge requirements.
Can electrostatic discharge technology extend emptying intervals?
Traditional solutions remove grease that has already adhered – but do not address the reason why grease accumulates so quickly.
What is Power2Air/Grease, and how does it work?
H2O Shift's Power2Air/Grease is designed to work directly in the wastewater system upstream of the grease trap. The technology uses electrostatic discharge to break the bond between grease and organic material, preventing the grease from clumping in the separator or ventilation system. In practice, this can extend the emptying interval from typically 14 days to up to 3 months – without compromising the cleaning efficiency.
Power2Air/Grease is compatible with grease traps that comply with DS/EN 1825-1 and DS/EN 1825-2, and requires no chemicals, no filters, and no ongoing maintenance of the unit itself.
What does electrostatic discharge do to grease?
Electrostatic discharge neutralizes the bond between grease molecules and organic material. This means that grease precipitates in the grease trap instead of forming clumps in the system. The result is fewer emptyings, lower operating costs, and an installation that operates closer to its original capacity.
What does it do to operating costs?
Fewer drainings and cleaning visits reduce direct operating costs. Additionally, the company avoids the chemical and filter burden otherwise associated with traditional preventive solutions. There are no consumables associated with the Power2Air/Grease unit itself.
Installation and maintenance
Which installation requirements apply?
Installation should follow the manufacturer's instructions as well as the requirements of DS 432:2020 and Pipeline Centre Guideline 005. This includes correct placement in relation to wastewater sources, secure connection to the sewerage system, and necessary sludge trap capacity.
How often does it require maintenance?
Emptying frequency depends on load and capacity. In a busy restaurant kitchen, 14-day intervals are not uncommon. With electrostatic discharge technology, users report intervals of up to 3 months. Regardless of the technology: maintain a logbook system for emptying – it is crucial documentation for regulatory inspections.
Frequently asked questions
What is the difference between gravity-based and mechanical grease traps?
Gravity-based grease traps allow grease to float up and be collected. They are often cheaper and simpler to maintain. Mechanical separators use automation and handle larger quantities of grease, but require more maintenance.
How do I ensure my grease trap complies with regulations?
Ensure the separator has the necessary certifications (DS/EN 1825-1 and DS/EN 1825-2). Stay updated on local wastewater requirements. Perform regular emptying and document them.
What is a sludge trap, and is it mandatory?
A sludge trap is a pre-chamber that retains solid particles before the water reaches the grease trap. It is mandatory according to DS 432:2020 and DS/EN 1825-2 and must be emptied regularly.
Can Power2Air/Grease be installed on my existing grease trap?
Yes. Power2Air/Grease is designed as a retrofit solution and can be integrated with existing installations that comply with DS/EN 1825-1 and DS/EN 1825-2. Contact H2O Shift for a specific assessment.
How do I ensure my wastewater complies with the discharge limit of 50 mg/l?
Sizing
First and foremost, a grease trap must be correctly sized. Grease traps vary in size and are measured in litres of wastewater per second – this is the amount of wastewater the separator can sufficiently slow down to separate the grease from the water.
A technician inspects all pipes and kitchen elements that send greasy wastewater to the grease trap, and then provides a recommendation for the correct size. Typical standard sizes are:
- 2 l/s
- 4 l/s
- 7 l/s
- 11 l/s
- 14 l/s
In special cases, custom-made grease traps for larger quantities of grease may be required. If the kitchen's output exceeds what the grease trap can physically separate, the separator should be replaced or alternative solutions considered.
Emptying
A grease trap should be bottom-emptied, flushed, and refilled with water before kitchen production restarts. According to DS/EN 1825-2, this should be done every 14 days or monthly.
Unfortunately, incorrect emptying is a widespread problem:
- Incomplete bottom emptying – means that the flows through the tank do not function correctly, even after emptying has been carried out.
- The tank does not fill up with water after emptying – a significant amount of grease flows directly into the sewage system until the tank fills up again during operation, which creates problems in the sewage system
- Grease crusts – if the grease layer has been present for a long time, hard crusts can form that can only be removed manually. If not cleaned properly, the grease trap loses its function, and the grease flows unhindered into the sewer system.
Conclusion
The right choice of grease trap is crucial for regulatory compliance and stable operation. Correct sizing, the right standards, and a well-developed sludge trap are the foundation. On top of that, electrostatic discharge technology like H2O Shift's Power2Air/Grease can reduce grease accumulation at the source and extend emptying intervals from 14 days to up to 3 months – without chemicals, filters, or ongoing unit maintenance. Contact H2O Shift for an assessment of how the technology fits your installation.
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