Passive trap installation and maintenance


These instructions apply to MACTRAP Polymer 250-3000 litre units.

MACTRAP Polymer Grease traps are not loadbearing* and require care during installation.

Check which size that best suits your application.

It is preferable for grease traps to drain by gravity to the sewer, so ensure a good flow allows this.

Plumbing and drainage must comply with G13 Foul Water code and the Australian and New Zealand Standard (AS/NZS 3500).Set plumbing at trap as per specification diagram supplied with tank.

Location: Install the grease trap in a location that is accessible by manual or vacuum tanker so it can be cleaned out. Keep regularly cleaned.

Inside Installation-Ensure it is permitted by local Authority and located in a permitted place, with easy cleaning access. Sit the trap on a firm surface capable of holding 225 Kg to 1100 Kg depending on litre capacity of model used and secure firmly to wall with builder frame or strap brace.

Outside Installation- All MACTRAP Passive traps can be installed above or below ground subject to herein conditions: Outside installation is recommended in all possible situations.

Above ground - locate on firm surface and attach to wall or support to prevent moving or tipping. Allow room above unit for removing lid and cleaning service. MACTRAP polymer units are 65C compliant so ensure water is cooled to <65C for continuous inflow. In very exposed hot sunny places or operations with hot water dishwashers or combi-ovens a support brace along the length of the trap should be incorporated to reduce risk of bulge. Provide shade for excessive hot sun and cover for frosts.

*Below ground, we recommend the MACTRAP HDPE Polymer is used for underground installations. Ensure the base is flat and firm. For larger units (1500L to 3000L) it is critical that the base is flat with even compaction to ensure no distortion (bend) in the base of the tank.  Lay trap level and vertical on firm base with 25mm sand underneath for stabilising base. Cut hole as close to size as possible and back fill with sand, light compaction only. Leave lid exposed for access and service.

Traffic areas or pedestrian traffic areas: For the entire MACTRAP range we offer CLASS A Polymer,  and Class B and Class D steel lid with a variable height riser. The MACTRAP cover fits over the riser and is settled into the load bearing concrete pedestrian or traffic strata above. These are to be inserted in the concrete or other surround. An engineer’s detail is required to ensure the risers and cover plates are set and located on a substrate that will hold the appropriate class cover. This means a concrete surround or steel frame to engineer’s requirement installed above the grease trap to take traffic weight. For 500L and larger tanks, we recommend 2 risers for cleaning and servicing. If desired, an optional 3rd riser can be added. Note loading detail in specific size spec sheet.

If setting the tank top below 450mm with risers, a load bearing plate (concrete recommended) should be placed on top of a 50mm sand layer and set before backfilling to concrete surface layer. (Refer to specification sheet).

Contact us for riser and cover plate options and details


All connections are for 100mm sewer/drainage pipe. Reductions are installer’s option.

Inlet connection: For the polymer traps connect with appropriate quick coupler. Or if fitted with “Wallace” or “Uniseal” seal, insert 100mm appropriate grade pipe directly into seal and affix the internal pick-ups as shown in product specification drawing. Inlet pipe should not exceed 7.6m from source of FPG without heat trace or high fall rate (check with Engineer) to avoid pre-trap blockages.

MACTRAP  Grease separators have a default 100mm SW PVC inlet and outlet socket for ease of connection. If required, to slow Inlet flow rate (to ensure steady non swirl inflow) a reducing socket can be applied but ensure invert is correct. Contact MACTRAP for information if required.

Inlet piping

Wastewater entering a grease separator from the kitchen must do so in a calm manner in order to not agitate the sludge and grease layers inside the separator. Down pipes from the kitchen should be connected to the horizontal pipe with two 45-degree fittings (1) with at least 250 mm between the two fittings (2) (no 90 degree fittings should be used). No downward pipes should be connected to the main separator inlet pipe immediately prior to entering the separator.

For a separator with a Ø 100/110 inlet, no downward connection should be made within 1 meter of the inlet to the grease separator - for a Ø 160 inlet a 1.5-meter distance should be observed (3) - for a Ø 200 inlet a 2.0 meter distance should be observed. Separator inlet pipes should be laid with at least a 2% (1:50) slope to the separator. In the case that the main inlet pipe is laid through cold rooms or underground, equipping this pipe with insulation or a heating system equipped with a thermostat should be considered.

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Inflow restriction will be required if inlet  is directly down to the MACTRAP tank

Outlet connection: If using our polymer trap connect with appropriate 105-112mm quick coupler. “Wallace” seals, insert 100mm appropriate grade pipe directly into seal and affix the internal pick-ups as shown in the specification drawing. Do not damage Wallace seal.

The invert level of the inlet and outlet are set. Refer to product specification diagram. Do not raise or lower.

If the invert of the outlet is too high the inlet connection may be submerged.  

The invert of the outlet pipe must be lower (10mm to 150mm) than the invert of the inlet pipe.

Outlet pipe must never be less diameter than the inlet.

If the invert of the outlet is too high the inlet connection may be submerged.

Inspection and testing: Check local requirements as they may vary. It is recommended that a lidded inspection (typical Marley type T section with screw cap pre-inlet or post-outlet chamber be fitted on inlet and outlet. These can be set to the invert levels. Ensure good access. Check and clean regularly to avoid malodour. Do not allow FOG build up to exceed 50% outlet pipe diameter.

Backflow prevention: Can be mitigated by installing a backflow prevention device within five metres of the grease trap. Check local regulations.

Venting: All polymer MACTRAP grease traps must be vented off either inlet or outlet, close to the tank to ensure good ventilation. If any doubt a hole can be cut on the top of the tanks and a skin fitting inserted to take a vent directly off the tank top or between risers if underground.  If installing a vent off the lid, install a 50-100 mm vent (depending on local requirement) on the lid with skin fitting or appropriate Wallace seal. For cross ventilation install one at each end of the grease trap above the water line. If the outlet is direct to sewer then a vent on outlet may be required. On MACTRAP polymer traps the installer should drill a hole size to suit the spigot in a position that suits (one at each end of the lid) to ensure air flow over FOG at all times. Ensure air space above FOG is well ventilated to meet council requirements. (Check what your local requirements are).

Safe access: All above ground grease trap Installations will require secure fixing to wall or other secure means and safe access to inspect and maintain the grease trap.

Inspections: Following installation arrange an Inspection by a Plumbing and Drainage Inspector.

This is to ensure that the pipe-work is installed according to AS/NZS 3500 and G13 3.4

Vertical clearance: Ensure there is vertical clearance above the grease trap to allow access, lid removal and cleaning.  If possible have clearance at least the maximum depth of the grease trap.

Lids: Install lids securely to prevent leakage and odour. Lock where possible.

Gully: The grease trap is not to be used as a relief overflow point. Install a gully in addition to the trap and a running trap if part of a stacked line.

Reflux valve: If problem arises consider installing a reflux valve if: the difference in levels between the overflow level of the lowest fixtures and the top of the relief gully is less than 50-150 mm.

In-sink trap: The grease trap is not a waste disposal unit, and if used as one will require regular cleaning. A primary solids trap should be fitted prior to grease trap for this purpose.

Passive Grease traps are usually not permitted for installation in kitchen or food areas - please check with your local authority as to local requirement. Please remind the customer to check with your local authority regarding local requirements for discharging trade wastewater to the sewer.

Always obtain and follow the manufacturer’s instructions for correct installation.

Additional installation information:

For schematic instructions showing refer to specification diagrams. For other information contact or phone 07 549 0414 / 0274 978 791 or visit our website's relevant product page. 



The MACTRAP polymer grease trap plastic is warrantied for 20 years as to impermeability, fitness for use and structural stability. The manufactured unit is warrantied for 5 years provided installation and operation are per the specifications provided with each unit. MACTRAP expressly states that wear and tear is not a defect and the same applies to defects from defective servicing.

The MACTRAP Polymer grease traps have flexible Wallace seals to ensure long life of the main inlet and outlet connections as well as flexibility with water tightness in ground movement. MACTRAPs can be installed above or below ground.

Whilst this product is highly robust, care is required to ensure long life.

Water temperature: The MACTRAP polymer grease trap is certified to operate with water temperatures to 65C. Higher continuous temperatures may cause sagging.

Venting: It is important the top of the tank is vented and the installation not under compression or incurring traffic both pedestrian and vehicular without the correct optional cover plates installed.

Chemicals: The MACTRAP polymer grease trap is tested to handle most kitchen factory type chemicals especially as they are usually diluted with water. It is however not recommended that pure benzene and highly concentrated sulphuric acid in raw form are not used.

Clean-out: When the grease trap is being used, the frequency of clean out (usually vacuum extraction) is totally dependent on how much fat, oil and grease the operator is putting into it. Remember grease traps are not a rubbish bin so the more solid rubbish pre-removed (i.e. sink filters) will allow the grease trap to function at its highest efficiency.

Under normal usage, MACTRAP recommends at least two clean outs per year in relation to trap size, however heavy use or excess solids may require more frequent clean outs.