If your Melbourne business has a commercial kitchen, food preparation area, mechanical workshop, or any operation that produces oily or greasy wastewater, you almost certainly need a grease trap — and a compliant liquid waste management system to go with it. Grease traps and liquid waste are among the most overlooked aspects of commercial waste management, yet the consequences of getting it wrong are severe: blocked sewer mains, EPA fines of up to $363,000 for companies, and trade waste agreement cancellations that can force a business to shut down.
What Is a Grease Trap and Who Needs One?
A grease trap captures fats, oils, and grease (FOG) before they enter the sewer system. It slows the flow of wastewater, allowing FOG to float to the surface and solids to settle to the bottom. The relatively clean water in the middle passes through to the sewer.
In Melbourne, any business that discharges trade waste needs appropriate pre-treatment. Businesses that typically require grease traps include restaurants, cafes, takeaway outlets, hotels with commercial kitchens, hospitals and aged care facilities with on-site catering, food manufacturing plants, supermarkets with preparation areas, school canteens, and automotive workshops (which use oil-water separators).
Melbourne's Trade Waste Framework
Trade waste discharge to the sewer is regulated by Melbourne Water and the three retail water companies: Yarra Valley Water, South East Water, and Greater Western Water. To legally discharge trade waste, your business needs a Trade Waste Agreement (TWA) with your local water retailer.
A TWA specifies what you can and cannot discharge, the pre-treatment required, and any monitoring obligations. Operating without a TWA — or in breach of its conditions — can result in penalties, forced disconnection, or prosecution. Key requirements include appropriately sized grease traps, regular pump-outs at specified intervals, maintenance records kept for a minimum of two years, and pump-outs performed by licensed liquid waste transporters registered with EPA Victoria.
Pump-Out Schedules and the 25% Rule
How often you need to pump out depends on grease trap size and the volume of trade waste produced. As a general guide for Melbourne food businesses:
- In-ground grease traps (1,000-5,000L): Every 4-8 weeks for busy restaurants, every 8-13 weeks for lower-volume operations
- Under-sink grease traps (40-100L): Every 1-2 weeks, typically cleaned by staff
- Large interceptors (5,000L+): Monthly for high-volume manufacturers, quarterly for lower-volume operations
The critical threshold is the 25% rule: your grease trap should be pumped when the combined depth of floating FOG and settled solids reaches 25% of the trap's liquid depth. Many trade waste agreements mandate this. Exceeding it reduces trap efficiency and risks FOG passing through to the sewer, which can breach your trade waste conditions and trigger enforcement action.
What Liquid Waste Pump-Outs Cost in Melbourne
Costs vary significantly depending on trap size, location, and provider. Rough guide for 2025:
- 1,000L grease trap: $250-$450 per service
- 2,000L grease trap: $350-$600 per service
- 5,000L+ grease trap: $600-$1,200+ per service
- Emergency or after-hours: 50-100% surcharge on standard rates
A busy restaurant with a 1,000L trap pumped every four weeks spends $6,500-$11,700 per year on grease trap maintenance alone. This is a significant cost category — and one where many businesses overpay without realising it. We routinely see price variations of 30-50% between providers for identical services.
Common Mistakes That Cost Money
Pumping on autopilot. Some businesses are locked into schedules set by their provider regardless of actual need. If your trap is consistently well below the 25% threshold at pump-out time, you may be able to extend your interval and save hundreds per year.
Not reviewing rates. Many businesses stick with whoever was first recommended when they opened, without ever shopping around. Getting three quotes annually takes minimal effort and can save thousands.
Ignoring under-sink traps. Small under-sink traps need daily attention — a five-minute staff job that is frequently neglected. Neglected under-sink traps overflow into the main trap, increasing pump-out frequency and costs.
Pouring FOG down the drain. Staff education is critical. Cooking oil should be collected in drums for recycling (many cooking oil recyclers collect for free). Food scraps should be scraped into bins before washing. These habits reduce grease trap load, extend pump-out intervals, and prevent expensive blockages.
Choosing a Liquid Waste Provider
When selecting a provider, verify EPA Victoria registration (all liquid waste transporters must be registered), ask for disposal documentation showing where waste was legally disposed, get transparent all-inclusive pricing (beware of hidden surcharges for travel time, waiting, or disposal), and ensure they offer flexible scheduling that does not disrupt your operations.
Beyond Grease Traps
Grease traps are the most common liquid waste concern, but other streams requiring licensed management include septic tank waste, wash bay water from automotive businesses, coolant and cutting fluids from manufacturing operations, and chemical waste from laboratories that may require prescribed industrial waste handling.
How Bundle Waste Can Help
Liquid waste is one of the areas where businesses consistently overpay. At Bundle Waste, we audit your liquid waste arrangements, benchmark costs against current market rates, and negotiate better deals with licensed providers. If you spend more than $5,000 per year on grease trap pump-outs, there is almost certainly room to save. Contact us for a free assessment.
