How often commercial grease traps need cleaning in Perth, the 25% rule, real 2026 pricing guidance, and how to pick a licensed Controlled Waste Carrier.
BY FREMANTLE RESOURCE SOLUTIONS · 10 MIN READ · UPDATED JUNE 2026
Grease Trap Cleaning Perth: A Complete Guide for Commercial Sites in 2026
Quick answer. Commercial grease traps in Perth need to be pumped out by a licensed Controlled Waste Carrier before they reach 25% of their total liquid depth. Most restaurants and cafés need a service every four to twelve weeks; high-volume kitchens often need monthly. You cannot legally empty a commercial grease trap yourself in Western Australia. The waste must be transported by a carrier licensed by DWER under the Environmental Protection (Controlled Waste) Regulations 2004.
If you’re a Perth food business owner, café manager, hotel operator, or facilities manager who needs the practical detail, this guide walks through the WA-specific rules, the signs your trap needs servicing, real cost ranges, the actual cleaning process, and how to choose a licensed cleaner. Written by the team at Fremantle Resource Solutions.
IN THIS GUIDE
- What is a grease trap (and why every commercial kitchen has one)
- The 25% rule explained (and why most Perth operators get it wrong)
- How often should you clean a grease trap in Perth?
- Signs your grease trap needs cleaning right now
- The grease trap cleaning process: what actually happens
- What grease trap cleaning costs in Perth
- Common grease trap problems and what they mean
- Is DIY grease trap cleaning legal in wa?
- How to choose a licensed grease trap cleaner in Perth
- Practical tips to extend the time between cleans
- Frequently asked questions
70+
Years Serving Perth & Fremantle
T00004
DWER Controlled Waste Licence
25%
Water Corp Fill Threshold Rule
SECTION 01
WHAT IS A GREASE TRAP (AND WHY EVERY COMMERCIAL KITCHEN HAS ONE)
A grease trap, sometimes called a grease arrestor or grease interceptor, is a plumbing device that sits between the dirty water leaving your kitchen and the public sewer. Its job is to cool the wastewater down so the fats, oils and grease (FOG) float to the top, the solids sink to the bottom, and only relatively clean water leaves through the outlet.
The trap works because of physics, not filtration. Hot greasy water flows in, the temperature drops, the grease cap forms on top, food solids settle at the base. Over time the grease cap thickens and the solids layer rises. When the combined depth of FOG plus solids reaches around 25% of the total trap depth, the device starts losing efficiency. Beyond that, grease begins spilling through to the sewer with the wastewater.
Water Corporation in Perth requires every commercial premises that produces FOG to install and maintain a grease arrestor. Without one, you can’t legally connect your commercial kitchen to the sewer.
A quick note on terminology. In WA the technically correct term is ‘grease arrestor’, which is the term Water Corporation uses in its Trade Waste rules. ‘Grease trap’ is more common in everyday speech and across the rest of Australia. Both refer to the same device.
SECTION 02
THE 25% RULE EXPLAINED (AND WHY MOST PERTH OPERATORS GET IT WRONG)
Western Australia’s grease trap rules are governed by Water Corporation’s Trade Waste Compliance Code and the Environmental Protection (Controlled Waste) Regulations 2004. The critical rule is this:
A grease trap must be pumped out before the combined depth of FOG and solids exceeds 25% of the total liquid depth.
What that does not mean:
- It does not mean “clean it every three months automatically”.
- It does not mean “wait until it overflows”.
- It does not mean “as needed if there’s a smell”.
What it actually means: you need to know how fast your trap fills, and schedule service before it hits the 25% threshold. A 1,500L grease trap servicing a 70-cover suburban café might need quarterly pump-outs. A 1,500L grease trap servicing a 200-cover fast-casual restaurant with deep fryers might need fortnightly pump-outs. Same trap, very different schedules.
Water Corporation trade waste inspectors do check this. The penalty pathway is: notice of non-compliance first, then a fine (up to $5,000 per breach for businesses under WA Environment Protection Act provisions), then a disconnection notice if uncorrected. In serious or repeated breaches, the operator can be charged under the Environmental Protection Act 1986 (WA).
FRS licensed field crew on site in Perth.
SECTION 03
HOW OFTEN SHOULD YOU CLEAN A GREASE TRAP IN PERTH?
The honest answer is ‘as often as the 25% rule requires’, which depends on your trap size, your kitchen volume, what you cook, and how much FOG your menu produces.
Important: the actual required cleaning frequency for your site is determined by Water Corporation and stipulated on your trade waste permit. The intervals below are practical starting points, but the frequency listed on your permit is the compliance benchmark you must meet. If in doubt, check your permit or ask your carrier to review it with you.
For practical planning, here are the typical service intervals we see across Perth and Fremantle:
- Small café (under 50 covers, mostly cold food): every 12 to 16 weeks.
- Standard restaurant (50 to 120 covers, mixed menu): every 6 to 12 weeks.
- Fast food, fish & chips, deep fryer-heavy sites: every 4 to 6 weeks.
- High-volume restaurants and food courts: every 2 to 4 weeks.
- Hotel kitchens (multiple service periods per day): every 4 to 8 weeks.
- Aged care and hospital kitchens: every 6 to 8 weeks.
- Bakery (limited FOG, still requires an arrestor): every 12 to 24 weeks.
- Function venues, breweries with food service: every 4 to 8 weeks.
These are starting points. We tell every new client: book the first service, then on the day of that service we measure the FOG and solids depth. From that we calculate your specific fill rate and set your service interval so you stay safely under the 25% threshold without paying for services you do not need.
SECTION 04
SIGNS YOUR GREASE TRAP NEEDS CLEANING RIGHT NOW
Even with a scheduled service in place, situations come up that mean an unscheduled pump-out:
- Slow-draining floor wastes or sinks. Grease has reached the inlet and is restricting flow.
- Sewer smell in the kitchen or near the trap. The water seal in the trap is compromised, usually because grease has displaced too much water.
- Grease cap visible at the inlet baffle. If you can see solid grease at the top of the inlet pipe, you’re well past 25%.
- Backups in the dishpit or floor drains. Wastewater is being pushed back up because the trap can’t accept new flow.
- Recent menu or volume change. New deep fryers, longer trading hours, or extra service periods will fill the trap faster than your old schedule allows.
- Trade Waste inspector visit. If Water Corporation has been past, you may need an immediate pump-out and certificate.
If any of these happen, book an emergency clean. Continuing to operate a grease trap that is over the 25% mark exposes the business to fines and pushes grease into the council sewer, which can trigger a separate clean-up bill from Water Corp.
SECTION 05
THE GREASE TRAP CLEANING PROCESS: WHAT ACTUALLY HAPPENS
A typical commercial grease trap clean in Perth takes 45 to 90 minutes for an in-ground trap. The process is the same whether you have a 100L unit under the sink or a 5,000L below-ground arrestor.
STEP 01
Site Arrival & Isolation
Licensed operator arrives in a marked vacuum tanker. They isolate the area, place safety signage, lift the access cover and assess depth and condition. A laser depth gauge or dip stick measures the FOG plus solids percentage.
STEP 02
Full Removal
All contents are pumped from the trap. That is water, grease cap, settled solids, the lot. A full pump-out is the only way to reset the 25% clock. Skimming the top is not compliant.
STEP 03
Internal Clean & Scrape
Once empty, the operator scrapes the walls and baffles, removing hardened grease that the vacuum couldn’t lift. Any food solids stuck in the inlet and outlet baffles are cleared.
STEP 04
Visual Inspection
With the trap empty, the operator checks for cracking, baffle damage, displaced lids, and inlet/outlet pipe condition. Anything that needs repair is documented.
STEP 05
Refill & Reseal
The trap is refilled with clean water to re-establish the water seal, the lid is replaced, and any disturbed area is cleaned down.
STEP 06
Compliance Paperwork
The operator issues a Controlled Waste Tracking Form (also called a CWT) showing waste type, volume, generator (your business), carrier (the cleaner) and destination (an approved facility). Keep this on file. Water Corporation inspectors can ask for two years of CWT records.
Then, Transport to licensed disposal. The waste is taken to a DWER-approved facility for processing. It cannot be dumped, mixed with general waste, or returned to land.
If you are getting quotes from cleaners and someone offers a no-paperwork or skim-only service, walk away. That service is not compliant in WA.
Purpose-built vacuum tanker used for FRS grease arrestor pump-outs.
SECTION 06
WHAT GREASE TRAP CLEANING COSTS IN PERTH
Costs vary by trap size, location and access. The main factors are how big your trap is, where it sits on site, whether the truck can get close, and whether it’s a scheduled visit or an emergency call.
As a Perth pricing guide for 2026:
| Trap size | Typical cost per service |
| Under 200L (under-sink) | $180 to $320 |
| 500 to 1,000L | $280 to $480 |
| 1,500 to 2,000L | $380 to $650 |
| 3,000 to 5,000L | $550 to $1,100 |
| Above 5,000L | Quoted on site |
The best way to get an accurate figure for your site is to request a written quote from a licensed carrier. A reputable operator will ask about trap size and volume, review site access, and come back to you with a clear scope and price in writing rather than a rough phone estimate.
Things that add cost:
- After-hours service (typically adds 30 to 60%).
- Difficult access: long hose runs from the truck, locked car parks, narrow alleys, height obstacles.
- Emergency response (same-day or out-of-hours).
- Heavy solids requiring high-pressure jetting.
- Damaged baffles or lids that need replacement.
Things that reduce cost over time:
- Booking a regular service contract rather than ad-hoc calls.
- Proper kitchen practices: scrape plates to the bin, no fryer oil down sinks, dry-wipe pots before washing.
- Installing or maintaining a pre-strainer to catch food solids before they reach the trap.
A scheduled contract usually drops the per-service cost 10 to 20% versus ad-hoc bookings, and removes the late-Friday-night panic call when the kitchen backs up before service.
GET YOUR GREASE TRAP SORTED IN ONE CALL
Tell us your site type and trap size. We come back with a written quote, a Water Corp-aligned service interval, and the consignment paperwork that protects your business.
SECTION 07
COMMON GREASE TRAP PROBLEMS AND WHAT THEY MEAN
- Persistent foul odour. Almost always one of two things: grease cap is too thick, or the water seal in the trap is broken because grease has displaced it. Both are fixed by a full pump-out and reseal.
- Slow drains after a recent clean. Suggests the inlet baffle is partially blocked with hardened solids that the cleaner didn’t fully clear. Call them back. A reputable cleaner will return at no charge.
- Trap fills faster than expected. Either kitchen volume has increased, the menu has shifted to more FOG-heavy items, or the upstream plumbing is missing a pre-strainer that should be catching food solids.
- Visible grease in the outlet pipe. T The trap is failing. Either it is grossly under-sized for your volume, or it has been allowed to overflow at some point and the outlet baffle is fouled. Get it inspected; you may need a larger unit.
- Cracked or distorted trap walls. Older concrete or fibreglass traps fail eventually. A cleaner will spot this during the empty inspection. Do not ignore. Once a trap leaks, you are discharging untreated FOG-laden water into the ground, which is an EPA reportable event.
- Constant trade waste inspector visits. Water Corp is telling you something. Either your records aren’t up to date, your schedule isn’t aggressive enough, or someone has reported a sewer issue traced back to your site.
SECTION 08
IS DIY GREASE TRAP CLEANING LEGAL IN WA?
For commercial premises, no. The Environmental Protection (Controlled Waste) Regulations 2004 require grease trap waste (categorised as N205 putrescible/organic waste) to be transported by a Controlled Waste Carrier licensed by DWER and disposed of at an approved facility.
A business owner cannot legally:
- Pump the trap and pour the contents into the sewer.
- Bag the solids and put them in general waste.
- Dispose of grease cap material in council green bins.
- Tip waste at a site that is not approved for controlled waste.
The licensed cleaner’s truck has a DWER carrier number painted on it for a reason. Without that licence, the transport itself is illegal.
For domestic septic systems or residential greywater traps different rules apply, but if you are operating commercially, the only compliant route is a licensed Controlled Waste Carrier.
SECTION 09
HOW TO CHOOSE A LICENSED GREASE TRAP CLEANER IN PERTH
Five questions to ask before you book.
- What’s your DWER Controlled Waste Carrier licence number? Any compliant cleaner will tell you immediately and the number will be on their truck. If they hesitate, move on.
- Will I receive a Controlled Waste Tracking certificate after every service? The answer should be “yes, by email within 24 hours” or “we leave one on site.” If they say “we do not do paperwork,” that is a red flag.
- Where is the waste disposed? They should be able to name the approved facility. In Perth this is typically Welshpool, Henderson or Forrestdale.
- What is your standard response time for emergencies? A good operator will commit to 2 to 4 hours for urgent calls in the metro area.
- Can you measure my trap’s actual fill rate and recommend an interval? A real operator will measure and recommend, not just sell you a quarterly contract sight unseen.
You also want to look at:
- Length of time in business (longer means more accountable)
- Whether they handle other liquid waste in case your operation expands (septic, hydrocarbon, waste oil)
- Whether they can do emergency response 24/7, and
- Whether they’re insured for site work in your building type (hospitality, healthcare, industrial).
Fremantle Resource Solutions has been a licensed Controlled Waste Carrier in WA since 1952 (DWER licence T00004). We service grease arrestors from 100L under-sink units up to 30,000L industrial arrestors across Perth, Fremantle and the surrounding regions, with same-day and out-of-hours availability for urgent calls.
Onsite compliance measurement, cleaning and paperwork in one visit.
SECTION 10
PRACTICAL TIPS TO EXTEND THE TIME BETWEEN CLEANS
Even with a scheduled service, you can stretch the interval (and save money) with good kitchen habits:
- Scrape plates to the bin, not the sink. Food solids are the bulk of what fills the bottom of the trap.
- Dry-wipe oily pots before washing. Wipe excess oil into the bin with paper towel before the pot enters the dishpit.
- Never pour fryer oil down a sink. Used cooking oil is a separate waste stream. Most reputable Perth waste companies collect waste oil for biofuel processing.
- Install a pre-strainer in your floor wastes. A simple stainless mesh in the floor waste catches a surprising amount of food solid before it reaches the trap.
- Hot water at the sink, cool water through the trap. Avoid running long volumes of very hot water through the system. It keeps grease in solution past the trap and into the sewer, which Water Corp does not appreciate.
- Train new kitchen staff. Most grease trap problems trace back to one team member tipping prep waste down the sink during a busy service.
These habits do not eliminate the need for scheduled cleaning, but they meaningfully change your fill rate.
MAKE COMPLIANCE THE EASY PART OF YOUR KITCHEN
Get a licensed Controlled Waste Carrier looking after your grease arrestor from the first service. Measured fill rate, Water Corp-aligned schedule, paperwork on time, every time.
FAQ
FREQUENTLY ASKED QUESTIONS
Forty-five minutes to ninety minutes for most commercial traps. Very large arrestors (above 5,000L) or units with heavy solids can take longer.
For most under-sink units no. The trap is offline for the actual pump-out (typically 15 to 20 minutes within the visit). For below-ground arrestors, dishpit and floor drains shouldn’t be used during the pump-out. We schedule outside service hours where possible.
In WA, Water Corporation uses ‘grease arrestor’ in its trade waste rules. ‘Grease trap’ is the more common everyday term. They are the same device.
No. The 25% rule applies to combined FOG plus solids depth, and the solids at the bottom are not removed by skimming. Compliance requires a full pump-out.
The trap continues filling. Once over 25%, grease starts spilling through to the sewer. Water Corp can detect this through their flow monitoring and trace it back to your premises. The consequence is a non-compliance notice, then a fine, then potentially disconnection.
No. The rule is the 25% threshold, not a calendar interval. The interval is whatever frequency keeps you under that threshold. Your cleaner should measure and recommend.
You need a DWER Controlled Waste Carrier licence to transport the waste. The cleaning activity itself doesn’t require a separate licence, but disposal of N205 waste outside an approved facility is an offence.
You will never solve the problem with more frequent cleaning alone. The trap will keep failing every few weeks. Get a sizing review. A new trap is usually $3,000 to $15,000 installed depending on size and access, and it pays for itself within 12 to 24 months in saved service costs and avoided non-compliance.
Yes. Most Perth Controlled Waste Carriers (us included) handle waste oil and grease trap waste together. Single visit, two waste streams, lower overall cost. See waste oil collection.
Two years of Controlled Waste Tracking certificates, your service contract, and any compliance notices from Water Corporation. Keep them in a folder near the kitchen pass for quick access during a trade waste inspection.