Frequency guide
How often should a grease trap be cleaned?
The honest answer: your water authority sets the frequency per venue, but here are the real-world ranges and the rule contractors use day-to-day.
The general rule, also called the 25 per cent rule
Most authorities and most contractors work to the rule that a trap should be pumped before the layer of fat, oil, grease and solids reaches 25 per cent of total trap depth. Past that point, the trap stops separating effectively, fats start to carry through into the sewer, and you risk an overflow.
In practice the 25 per cent rule translates to monthly to quarterly for most venues, which is also where most trade waste agreements land.
What changes your frequency
- Venue type and volume. Daily meals served drives load directly.
- Trap size relative to output. A 1,000-litre trap on a fryer-heavy kitchen fills four times faster than a 2,000-litre trap on the same site.
- Menu mix. Burger, fish and chips, and fried-chicken kitchens load traps far faster than a sandwich-led cafe.
- Pre-treatment. Strainers, dosing systems and grease-eating bacteria all stretch the interval if used correctly.
Typical frequency by venue type
These are starting points based on industry-standard load assumptions. The frequency in your trade waste agreement overrides them.
| Venue type | Typical interval | Notes |
|---|---|---|
| Busy restaurant or fast food | Monthly | High fryer load and fast solids build-up. Often monthly even on a larger trap. |
| Cafe or bakery | Every 1 to 3 months | Light meal volume but constant dairy and pastry residue. Quarterly is common. |
| Pub or club kitchen | Every 1 to 3 months | Variable, depends on whether the kitchen runs daily lunch or just weekend nights. |
| Small takeaway | Quarterly | Smaller traps, lower daily volume. A 1,000-litre trap on quarterly is the most common setup. |
| Hotel kitchen | Monthly to bi-monthly | Multiple service periods per day, breakfast through dinner. Treat as a high-load venue. |
| Aged care or school canteen | Every 2 to 3 months | Steady moderate load, predictable, contracts almost always pre-scheduled. |
Who sets the legal frequency
Your water authority writes a binding interval into your trade waste agreement. The figures above are practical defaults; the agreement is the rule. Pick your state for the regulator and the published penalty for missing a scheduled clean:
Frequently asked
- How often should a grease trap be cleaned in Australia?
- Most authorities and contractors work to the 25 per cent rule, meaning the trap is pumped before the fat, oil, grease and solids layer reaches a quarter of the total depth. In practice that is monthly to quarterly for the average venue. Your water authority sets the binding figure in your trade waste agreement.
- What sets the legal frequency?
- Your water authority. In NSW it is Sydney Water or Hunter Water. In Victoria it is the metro retailer covering your suburb. In Queensland it is Urban Utilities or Unitywater. Each writes a frequency into your trade waste agreement based on trap size and your fat, oil and grease load.
- Does the frequency change between summer and winter?
- Slightly. Hot weather speeds up the layer of solids and grease, so some authorities and contractors recommend tightening the interval over summer if your trap is borderline. The agreement frequency does not change month to month, but a contractor on a recurring schedule will often flag if your trap is loading faster than expected.
- Can I clean it less often than the agreement says?
- No. The frequency in your trade waste agreement is a legal minimum. Pumping less often than required is a breach. If you genuinely have a small load and want a longer interval, ask your water authority for a variation rather than skipping a clean.