Grease arrestor installation guidelines

Grease arrestors reduce the amount of greasy waste flowing into the wastewater system, by allowing fats, oil and grease to rise to the top and solids to sink to the bottom.

Grease arrestors must be installed by licensed plumbers according to our trade waste requirements and the manufacturer’s instructions. Incorrect installations can affect the ability to service the grease arrestor to the required standard and allow greasy wastewater to discharge to the wastewater system where it can cause blockages and overflows to the environment.

Installation

• We have specific requirements for grease arrestor sizing for the food handling and preparation industry.
• The walls and floor of grease arrestors must be impenetrable, and the inner surface acid resistant.
• Grease arrestors may be constructed, prefabricated or precast. The design, material used and size must be accepted by Water Corporation prior to installation.
• Where grease arrestors require baffles the minimum thickness is 19mm. Baffles constructed of uPVC or HDPE must be reinforced
• Gas tight covers to an arrestor are required where:
  • There is vehicular traffic
  • There is pedestrian traffic
  • The arrestor is subjected to stormwater intrusion
  • The arrestor is installed inside a building
  • Light duty gas tight lids are recommended when grease arrestors are installed above ground
• All below ground installations (inclusive of riser) cannot have an installed depth greater than 3 metres. Installed depth is measured from the deepest part of the arrestor body to the finished floor level.  Where installations greater than 3 metres are proposed, a formal Water Corporation Trade Waste plumbing assessment of the overall installation must first be made (and approved) to determine if the proposed installation is the most appropriate depth. 
• Ensure there is vertical clearance above the grease arrestor, greater than the maximum depth of the grease arrestor that allows servicing of the arrestor in accordance with our standards.
• All above ground grease arrestor installations are required to have a platform and steps manufactured to the latest version of AS 1657 (fixed platforms, walkways, stairways and ladders - Design, construction and installation) for safe access to inspect and maintain the grease arrestor.
• Fixed suction lines shall terminate with a camlock fitting and ball valve adjacent to the grease arrestor and also where there is appropriate access for the liquid waste contractor to park their vehicle. Fixed suction lines shall not connect directly onto a grease arrestor.
• Grease arrestors should be located exterior of the building wherever practicable. If installed in a garden bed, grassed area or the like, then final finish of the entire length and width of the cover base must be of solid material (preferably concrete) and finished to the top of the lid to allow safe opening of lid covers. 
• Grease arrestors in internal locations must have appropriately designed mechanical or atmospheric ventilation.   
• Where the proposed location of grease arrestors will create a confined space as defined by AS 2865 (Safe working in a confined space) then confined space signage compliant to AS 1319 (Safety signs for the occupational environment) must be in place.  Entry into a confined space must comply with AS 2865. 
• Where below ground installations require the use of risers, the maximum riser height shall not be more than 900mm from the top of the tank to the finished floor level.  Installations deeper than 900mm will reduce proper maintenance and cleaning of the grease arrestor.
• A hose tap should be installed within 6 metres of the arrestor and must have an appropriate testable backflow prevention device fitted as required by plumbing standards.
• The inlet connection cannot enter at the side of the grease arrestor.
• Sample points can not be used as a relief disconnector gully. Sample point design, location, accessibility must not constitute a health and safety risk in sampling any trade waste discharge. 
• Dishwashing machines and glass washers are not to discharge to grease arrestors.

Venting

• All trade waste grease arrestors are to be vented to atmosphere, refer to educt vent diagram within Typical Drawing HX33-10-00 - Grease Arrestor for details.
• Air admittance valves are not to be used on the grease arrestor vent or the sealed trade waste sampling point.
• Grease arrestor vents may be combined above the overflow levels of the highest fixture connected to the grease arrestors providing the resulting vent size is in the accordance with Table 8.5.6.2 published within the latest version of AS/NZS 3500.2.

Plumbing

All associated plumbing work is to comply with the Plumbers Licensing and Plumbing Standards 2000 (The Plumbing Regulations).