How Often Should Grease Traps Be Cleaned?
A practical guide to grease trap cleaning frequency for food businesses in Wollongong and the Illawarra — covering the key factors, common intervals by business type, and the signs that a trap needs attention sooner.
Why It Matters
Why Grease Trap Cleaning Frequency Matters
A grease trap only works while it has sufficient capacity to capture incoming fats, oils, and grease. As the trap fills with accumulated FOG and solids, the effective working volume decreases. Once the trap is too full, it stops intercepting grease effectively — and FOG begins to flow through into the drain system.
The consequences of an overdue grease trap can be immediate and disruptive: blocked drains, kitchen flooding, sewer odours throughout the premises, potential council notices, and in the worst case, forced kitchen closure until the problem is resolved.
Getting the cleaning interval right — not too frequent, not too infrequent — is both a compliance requirement and a basic operational safeguard.
Your Approval Conditions
Check Your Trade Waste Approval First
Before relying on general frequency guidance, check whether your trade waste approval from Wollongong City Council specifies a minimum cleaning interval. Many approvals do.
If your approval conditions specify a frequency — for example, "clean every four weeks" or "service at least monthly" — that requirement takes precedence. Falling below the specified frequency is a compliance breach, regardless of what the trap looks like.
Key Factors
What Determines How Often a Grease Trap Needs Cleaning?
No two commercial kitchens are the same. The right cleaning interval for a trap depends on several interacting factors.
Trap Size & Capacity
A small trap fills much faster than a large one, even in the same kitchen. A 100-litre under-sink trap in a busy cafe may need weekly or fortnightly cleaning, while a 2,000-litre in-ground trap in a similar operation might only need quarterly servicing.
Kitchen Volume & Trading Hours
The more meals produced and the longer the kitchen operates, the more FOG enters the trap per week. A kitchen trading seven days from breakfast through dinner produces far more grease than one operating lunches only, five days a week.
Types of Food Prepared
Deep-frying, heavy sautéing, and meat-heavy cooking produce significantly more FOG than lighter cuisines. A fish and chip shop will load a grease trap far more rapidly than a salad bar or juice cafe.
Staff Practices
How staff handle FOG matters. Scraping plates and pans before washing, avoiding the disposal of cooking oils down the sink, and using drain strainers all reduce the load on the trap and can extend cleaning intervals.
Trade Waste Approval Conditions
Many businesses have minimum frequencies written into their trade waste approval. This is the hard floor — regardless of other factors, the trap must be serviced at least this often.
Trap Condition & Design
An older or poorly designed trap may accumulate grease faster or be less efficient at separation than a modern interceptor. Condition and design can affect both how quickly the trap fills and how well it functions when partially loaded.
General Guidance
Common Cleaning Intervals by Business Type
The following are general reference intervals only — not legal requirements. Always check your trade waste approval for the conditions that apply to your specific business.
Every 4–6 Weeks
High-volume commercial kitchens — large restaurants, busy pubs and clubs, high-turnover takeaway outlets, food manufacturers, and any kitchen with a smaller trap relative to its output volume.
Every 6–10 Weeks
Moderate-volume kitchens — busy cafes, mid-size restaurants, hotel dining rooms, club kitchens, and school canteens with high student numbers.
Every 3 Months
Lower-volume operations — smaller cafes and delis, lunch-only establishments, office kitchenettes with commercial cooking, or businesses with larger traps relative to their FOG output.
Every 6 Months
Seasonal or low-volume operations — businesses that trade seasonally, low-output commercial kitchens, or operations with very large in-ground traps and minimal cooking of high-fat foods.
Warning Signs
Signs a Grease Trap Needs Cleaning Sooner
Even with a scheduled service interval, sometimes a trap needs attention before the next planned visit. Watch for these warning signs between services:
- Sewer or rotten-egg smell from kitchen drains or the trap area
- Slow drainage in one or more kitchen sinks
- Visible grease or FOG floating in nearby floor drains or gullies
- Gurgling or bubbling sounds from sink drains after use
- Grease visible around the trap lid or inspection covers
- Kitchen drain backup or pooling water
- Recent increase in kitchen trading volume or new menu items
If you notice these signs before your scheduled service, arrange an earlier clean rather than waiting. The cost of a reactive clean is lower than the cost of a blocked drain or council compliance notice.
Scheduled vs Reactive
Scheduled Servicing vs Reactive Cleaning
There are two approaches to grease trap maintenance — and they have very different outcomes.
Scheduled Servicing
A recurring service arranged in advance at a set interval. The trap is cleaned on a predictable schedule, records are maintained automatically, and problems are prevented before they develop. Typically more cost-effective per service than reactive cleaning.
Reactive Cleaning
Calling when a problem arises — odours, slow drains, or a visible overflow. Higher urgency rates often apply, the trap is usually in worse condition, and the risk of kitchen disruption or compliance issues is elevated.
Most food businesses benefit from a scheduled arrangement. Request a quote to set one up →
Arrange Grease Trap Cleaning for Your Wollongong Business
Send your business details — type of kitchen, approximate trap size, current or preferred service interval, and suburb — and we'll be in touch about setting up a grease trap cleaning schedule.
Request a QuoteCommon Questions
Grease Trap Frequency — FAQs
Frequency depends on trap size, kitchen output, food type, and any minimum interval in your trade waste approval. As a general guide: high-volume kitchens every 4–8 weeks; moderate-volume every 6–12 weeks; lower-volume or seasonal operations quarterly or six-monthly. Your approval conditions take precedence.
An overloaded grease trap will stop intercepting FOG effectively. Grease passes through into the drain system, causing blockages, slow drainage, backups, sewer overflow, foul odours, and potential compliance issues with your trade waste approval. In severe cases the kitchen may need to stop operating until the issue is resolved.
Many trade waste approvals specify a minimum service frequency as part of the approval conditions. Check your specific approval documentation from Wollongong City Council. If you are unsure of your approval conditions, contact the council's trade waste team directly. The conditions in your approval take precedence over any general guidance.
Often yes. Common signs include slow drainage in kitchen sinks, a sewer or rotten-egg smell from drains or the trap area, visible grease in nearby floor drains or gullies, and gurgling sounds from the plumbing. If you notice any of these, the trap is likely approaching or past its cleaning interval.
Related Pages
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