Replacing a grease trap is rarely as simple as swapping one tank for another, and Salisbury proved the point. A commercial food service operator had an ageing unit that no longer suited the premises. The catch was access, because no excavator could reach the work area to dig the new trench.
So the operator called Citi Industries to handle the grease trap upgrade as a do and charge project. The job hinged on one early decision: how to excavate a tight site without heavy machinery.
Project Overview
This grease trap upgrade replaced an old below ground unit with a new Halgan 1000-litre tank. Because the location blocked machine access, the team turned to vacuum excavation instead. That single choice shaped the method, the timeline, and the way the crew protected the existing services.
Beyond the dig, the work covered fresh drainage, a new sewer connection, venting, and a reinstated concrete surface. The brief also called for cleanouts, so future maintenance would stay straightforward.
Key scope items included:
- New Halgan 1000-litre below ground grease trap fitted with Class D lids
- Concrete scanning, cutting, and removal to open the trench for the new tank
- Vacuum excavation in place of machinery, chosen for the restricted access
- Decommissioning of the old grease trap, with the pump-out handled by others
- Trade waste drainage tying the existing line into the new trap
- A new sewer connection joining the trap to the external sewer
- A 100mm vent to atmosphere for the new trap and the trade waste line
- Trench and surround reinstated in 25MPa concrete, single mesh, broom finish
- One 15mm RPZD backflow valve mounted on the building wall near the trap
- Three cleanouts for future maintenance and jetting
Challenges
An old grease trap that has reached its limit puts a kitchen at risk of blockages and failed inspections. Under Urban Utilities trade waste guidelines, the replacement still has to meet current sizing and connection rules. A like-for-like swap therefore was never going to be enough.
Access was the headline problem. The work area simply could not fit an excavator, so the usual dig-and-drop method was off the table. As a result, the team specified vacuum excavation, which clears soil with high-pressure air or water and a powerful suction hose. This method reaches confined spots and exposes buried lines without striking them.
Tying the new tank into live services added a second layer. The existing trade waste line, the external sewer, and the surrounding slab all had to stay intact during the changeover.
Key constraints on this project:
- No machine access, which ruled out conventional excavation entirely
- Vacuum excavation required to dig safely around buried services in a tight area
- Old trap had to be decommissioned cleanly before the new one went in
- New connections needed to join an existing trade waste line and external sewer
- Reinstated concrete had to meet a 25MPa, single mesh, broom finish specification
Solutions
Citi Industries sequenced the upgrade to keep risk low and disruption short. Each phase below sets up the next.
Decommissioning and Opening the Trench
To start, the old grease trap was taken offline, with a separate contractor handling the pump-out. The crew then scanned the slab to map what lay beneath, cut the concrete, and removed it to form the trench. Scanning first matters, since an unseen pipe or cable can turn a routine cut into a costly repair.
Our grease trap design and installation work always begins with this kind of groundwork, because the dig dictates everything that follows.
Vacuum Excavation in a Tight Spot
Next came the excavation itself, which is where this job differed from most. Since no machine could reach the area, the team used vacuum excavation to break and lift the soil. The technique pairs a high-pressure jet with industrial suction, drawing spoil into a holding tank.
The payoff is precision. Rather than risk a strike with a bucket, the crew exposed the ground gently and worked around the live services. Consequently, the existing pipes stayed undamaged throughout.
Installing the Halgan Tank and New Connections
With the trench open, the new Halgan 1000-litre tank went in, complete with Class D lids rated for traffic. The team then connected the trade waste drainage from the existing line into the new trap. A fresh sewer connection carried treated flow out to the external sewer.
After that, a 100mm vent was run to atmosphere for both the trap and the trade waste line. Venting clears gas and odour, which keeps the system stable. You can review the full below ground grease traps range for sizing on comparable jobs.
Backflow Protection, Cleanouts and Reinstatement
Finally, the crew fitted a 15mm RPZD valve on the building wall near the trap. This backflow device blocks contaminated water from reaching the drinking supply. Three cleanouts were also installed, giving future technicians easy points for jetting and maintenance.
To close out, the team poured the trench and surround back in 25MPa concrete with single mesh and a broom finish. That spec gives a durable, slip-aware surface that matches a working commercial yard.
Final Outcome
A site that could not take a machine now holds a modern, compliant grease trap. Citi Industries finished the Salisbury upgrade in December 2025, leaving the kitchen ready to trade without drainage worries. As a result, the operator swapped an end-of-life liability for infrastructure built to current standards.
- New Halgan 1000-litre trap installed where no excavator could reach
- Vacuum excavation protected every buried service during the dig
- Trade waste and sewer connections tied in cleanly to the existing system
- Three cleanouts and an RPZD valve added for easy upkeep and backflow safety
Because the work followed Queensland regulated plumbing work requirements, the operator can rely on the result through future audits. The broom-finished slab leaves the yard looking complete rather than patched.
Need a Grease Trap Upgrade?
Upgrading a grease trap is often harder than installing a brand new one. The old unit, the live connections, and a working site all complicate the job at once. However, the right method turns a difficult replacement into a clean handover.
Citi Industries plans each upgrade around the site’s real limits, not the ideal ones. When access rules out machinery, vacuum excavation keeps the project moving safely. The team reads the site, protects what is already there, and reinstates the surface to spec.
If your grease trap is past its prime or your site fights every dig, talk to our trade waste team. We assess access, plan the method, and deliver the documentation a clean handover needs.
Call Citi Industries on 1300 002 484 to discuss your project.
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