Best practices for managing fats, oils, and grease in sewer networks
Fats, oils, and grease (FOG) are among the most persistent causes of sewer blockages, odour complaints, pump failures, and wet-weather overflows. Once these materials cool inside a pipe, they can adhere to the crown and walls, trap food solids, and gradually reduce hydraulic capacity. A blockage that begins outside one commercial kitchen can eventually affect an entire catchment. Learn more about Contact.
Effective control starts well before a vacuum truck arrives. Water authorities, trade waste officers, maintenance crews, and food businesses need a coordinated programme covering source control, inspections, cleaning, data collection, and enforcement. The strongest programmes treat grease management as an operational risk rather than an occasional drainage problem.
Australian conditions make this especially important. Busy café strips in Melbourne, restaurant precincts in Sydney, and large hospitality venues in Brisbane can produce sharply different loads across the week. In regional areas, long travel distances and limited contractor availability add pressure to preventative planning. The table below summarises the main sources and practical responses.
| FOG source | Typical sewer risk | Useful control |
|---|---|---|
| Restaurants and cafés | Grease deposits, odour, localised blockages | Correctly sized grease arrestor, dry clean-up, regular servicing |
| Food manufacturing | High-strength trade waste and process oils | Trade waste agreement, pre-treatment, sampling and load control |
| Households | Small but widespread discharge of cooking fats | Public education, collection schemes, drain-safe disposal |
| Pump stations | Floating grease mats and rag-bound deposits | Targeted inspections, wet-well cleaning, upstream source tracing |
| Sewer mains | Reduced capacity and repeat blockages | Risk-based CCTV, programmed jetting, hotspot mapping |
Find the sources before cleaning the pipe
A sewer blockage is often the visible result of a problem several hundred metres upstream. Crews should record the location, material, estimated volume, odour, pipe size, weather, and nearby land uses after every incident. Repeated deposits near food premises, shopping centres, hospitals, or industrial estates provide valuable evidence for targeted intervention.
Work order systems and geographic information systems can connect blockage history with trade waste records, grease arrestor locations, inspection results, and customer complaints. This makes it easier to distinguish a one-off discharge from a recurring source. A useful review also checks whether a recent change in tenancy, menu, production, or cleaning practice has altered the FOG load.
Professional networks can help teams compare approaches and keep up with operational developments. LABS of CWEA’s technical updates provide a relevant channel for water environment professionals following training, facility, and industry news. For Australian utilities, the same principle applies locally: share incident patterns across operations, compliance, customer service, and asset planning rather than leaving the issue with the jetting crew.
Control grease at commercial premises
Commercial kitchens should remove solid food scraps and cooled grease before washing equipment. Staff need suitable bins, scrapers, absorbent materials, and clear procedures for pans, trays, fryer maintenance, and spill response. Sending hot oil or emulsified detergent mixtures down a sink can move the problem downstream, where the material cools and sticks to the sewer.
Grease arrestors, grease traps, and other pre-treatment devices must be correctly sized for the premises’ flow and food production. A small café, a hotel kitchen, and a food processing site will have different peak discharges, cleaning cycles, and solids loads. Poorly sized equipment may appear compliant while still allowing excessive FOG into the network.
Servicing should follow actual risk rather than a generic calendar. Operators need to inspect the grease layer, settled solids, inlet and outlet condition, baffles, lids, and ventilation. Records should include pump-out dates, service provider details, waste volumes, defects, and corrective actions. In Australian trade waste systems, these records may support permit conditions and help a utility decide when a formal inspection or sampling visit is warranted.
Build a risk-based maintenance programme
Routine sewer cleaning is most effective when it is directed by evidence. Rank pipe sections according to blockage frequency, consequence of failure, diameter, gradient, access, proximity to waterways, and the presence of known FOG sources. A high-risk rising main or constrained CBD sewer may justify more frequent inspection than a larger gravity main with no incident history.
Hydro-jetting can remove deposits, but incorrect pressure, nozzle selection, or flow control can damage older assets or shift grease into a downstream bottleneck. Vacuum recovery should be planned where deposits are heavy. CCTV before and after cleaning helps confirm whether the obstruction has been removed and whether roots, fractures, displaced joints, or corrosion are contributing to the recurrence.
Pump stations deserve particular attention. Grease can form floating mats in wet wells, bind with wipes and rags, interfere with level sensors, and reduce pump efficiency. Staff should inspect pump wells during planned maintenance, check abnormal run times and starts, and trend energy use where that data is available. A sudden change in pump performance can signal a developing FOG or solids problem before an overflow occurs.
Use monitoring, education, and enforcement together
FOG control is more successful when customers understand the reason for each requirement. Simple messages such as “scrape it, bin it, wipe it” are easier for kitchen staff to follow than technical instructions alone. Posters, induction training, translated material, and short toolbox talks can reinforce correct practices during staff turnover, which is common in hospitality.
Household education also matters because many small discharges can create a substantial cumulative load. Councils and utilities can promote collection points for used cooking oil, explain why liquid fats should be cooled and placed in general waste where appropriate, and discourage the use of hot water as a supposed disposal method. Campaigns are particularly useful before holiday periods and large community events, when cooking volumes rise.
Where education fails, enforcement should be consistent and proportionate. Inspection findings, sampling results, repeat blockages, and incomplete pump-out records can support graduated responses under a trade waste agreement. The objective is to correct the source, recover avoidable costs where policy permits, and protect the network. Aggressive action without clear evidence can damage relationships, while weak follow-up allows the same discharge to continue.
Turn performance data into long-term resilience
A mature programme measures outcomes rather than activity alone. Useful indicators include FOG-related blockages per 100 kilometres of sewer, repeat incidents at the same address, pump-station cleaning frequency, response time, overflow events, and the percentage of commercial premises with current maintenance records. Comparing these measures by catchment can reveal where investment and field attention will have the greatest effect.
Utilities should also consider how FOG interacts with wider treatment and environmental goals. High organic loads, detergents, and industrial discharges can influence downstream treatment performance, while poor containment during maintenance can affect waterways and public amenity. Research into alternative treatment processes, including algae-based treatment, illustrates why sewer operations should be considered as part of the broader water cycle rather than in isolation.
A practical annual review brings together operations, asset management, trade waste, laboratory staff, communications, and finance. The group can assess whether cleaning frequencies remain justified, whether enforcement is reducing repeat events, and whether capital upgrades are addressing the actual cause. It can also identify training needs, such as confined-space procedures, sampling methods, customer inspections, or the safe handling of recovered grease.
The best programmes remain flexible. A new apartment development, a food market, a major construction project, or a change in industrial activity can alter the risk profile quickly. Clear escalation pathways allow crews to flag emerging hotspots, while reliable contractor arrangements ensure that urgent pump-outs and specialist inspections are available when required. Australian utilities may also need contingency plans for flood conditions, bushfire impacts, or holiday periods when access and staffing change.
FOG management works when every stage supports the next: businesses prevent avoidable discharge, inspectors verify controls, maintenance teams remove deposits safely, and asset managers use reliable data to plan. The key point to remember is that the cheapest blockage is the one prevented at the source, before grease enters the sewer and becomes everyone’s problem.